A10 Networks
Annual Report 2018

Plain-text annual report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 10-K (Mark One) x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2018 OR ¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-36343 A10 NETWORKS, INC. (Exact Name of Registrant as Specified in its Charter) Delaware (State or Other Jurisdiction of Incorporation or Organization) 20-1446869 (I.R.S. Employer Identification No.) 3 West Plumeria Drive, San Jose, California 95134 (Address of Principal Executive Offices and Zip Code) (408) 325-8668 (Registrant’s Telephone Number, Including Area Code) Securities registered pursuant to Section 12(b) of the Act: Title of Each Class Common Stock, $.00001 Par Value Name of Each Exchange on Which Registered New York Stock Exchange Securities registered pursuant to Section 12(g) of the Act: None. Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.     Yes   ¨     No    x Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.     Yes  ¨     No    x Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days .     Yes   x     No    ¨ Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files) .     Yes   x     No    ¨ Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§ 229.405 of this chapter) is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. x Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and "emerging growth company" in Rule 12b-2 of the Exchange Act. Large accelerated filer Non-accelerated filer ¨ ¨ Accelerated filer Smaller reporting company Emerging growth company x ¨ x If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. x Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).  Yes    ¨    No   x The aggregate market value of the registrant’s common stock held by non-affiliates of the registrant as of June 29, 2018 (the last business day of the registrant’s most recently completed second fiscal quarter) was approximately $254.7 million , based upon the closing sale price of such stock on the New York Stock Exchange. For purposes of this                                 disclosure, shares of common stock held or controlled by executive officers and directors of the registrant and by persons who hold more than 5% of the outstanding shares of common stock have been treated as shares held by affiliates. However, such treatment should not be construed as an admission that any such person is an “affiliate” of the registrant. The registrant has no non-voting common equity. As of February 28, 2019 , the number of outstanding shares of the registrant’s common stock, par value $0.00001 per share, was 75,050,848 . Portions of the registrant’s definitive Proxy Statement for the 2019 Annual Stockholders’ Meeting, which the registrant expects to file with the Securities and Exchange Commission within 120 days of December 31, 2018, are incorporated by reference into Part III (Items 10, 11,12, 13 and 14) of this Annual Report on Form 10-K. DOCUMENTS INCORPORATED BY REFERENCE   A10 NETWORKS, INC. ANNUAL REPORT ON FORM 10-K FOR THE YEAR ENDED DECEMBER 31, 2018 TABLE OF CONTENTS Forward-Looking Statements PART I Item 1. Item 1A. Item 1B. Item 2. Item 3. Item 4. PART II Item 5. Item 6. Item 7. Business Risk Factors Unresolved Staff Comments Properties Legal Proceedings Mine Safety Disclosures Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities Selected Financial Data Management’s Discussion and Analysis of Financial Condition and Results of Operations Item 7A. Quantitative and Qualitative Disclosures about Market Risk Item 8. Item 9. Item 9A. Item 9B. PART II Item 10. Item 11. Item 12. Item 13. Item 14. PART IV Item 15. Item 16. Signatures Financial Statements and Supplementary Data Changes in and Disagreements with Accountants on Accounting and Financial Disclosure Controls and Procedures Other Information Directors, Executive Officers and Corporate Governance Executive Compensation Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters Certain Relationships and Related Transactions, and Director Independence Principal Accountant Fees and Services Exhibits and Financial Statement Schedules Form 10-K Summary 1 Page 2 4 13 40 40 40 40 41 42 43 57 59 90 90 92 93 93 93 93 93 94 96 97                                           FORWARD ‑ LOOKING STATEMENTS This Annual Report on Form 10-K contains forward ‑ looking statements made pursuant to the provisions of Section 21E of the Securities Exchange Act of 1934. These forward ‑ looking statements are based on management’s current expectations and beliefs, including estimates and projections about our industry. The following discussion and analysis contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. The words “believe,” “may,” “will,” “potentially,” “estimate,” “continue,” “anticipate,” “intend,” “could,” “would,” “project,” “plan,” “expect,” and similar expressions that convey uncertainty of future events or outcomes are intended to identify forward-looking statements. These forward-looking statements include, but are not limited to, statements concerning the following: our ability to provide customers with improved benefits relating to their applications; • • • • • • • • • • • • • • • • • • • • • • • • • • our ability to maintain an adequate rate of revenue growth; our ability to successfully anticipate market needs and opportunities; our business plan and our ability to effectively manage our growth; our ability to timely file financial, periodic and current reports required by the Exchange Act; loss or delay of expected purchases by our largest end-customers; our ability to further penetrate our existing customer base; our ability to displace existing products in established markets; continued growth in markets relating to network security; our ability to timely and effectively scale and adapt our existing technology; our ability to innovate new products and bring them to market in a timely manner; our ability to expand internationally; the effects of increased competition in our market and our ability to compete effectively; the effects of seasonal trends on our results of operations; the timing and amount of our subscription revenue; our expectations concerning relationships with third parties; the attraction and retention of qualified employees and key personnel; our ability to achieve or maintain profitability while continuing to invest in our sales, marketing and research and development teams; variations in product mix or geographic locations of our sales; fluctuations in currency exchange rates; increased cost requirements of being a public company and future sales of substantial amounts of our common stock in the public markets; the cost and potential outcomes of litigation; our ability to maintain, protect, and enhance our brand and intellectual property; future acquisitions of or investments in complementary companies, products, services or technologies; our ability to effectively integrate operations of entities we have acquired or may acquire; and actions relating to the remediation of identified material weaknesses. These forward-looking statements are subject to a number of risks, uncertainties, and assumptions, including those described in Item 1A Risk Factors and elsewhere in this Annual Report on Form 10-K. Moreover, we operate in a very competitive and rapidly changing environment, and new risks emerge from time to time. It is not possible for our management to predict all risks, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements we may make. In light of these risks, uncertainties, and assumptions, the forward-looking events and circumstances discussed in this Annual Report on Form 10-K may not occur and actual results could differ materially and adversely from those anticipated or implied in the forward-looking statements. 2 You should not rely upon forward-looking statements as predictions of future events. Although we believe that the expectations reflected in the forward- looking statements are reasonable, we cannot guarantee that the future results, levels of activity, performance or events and circumstances reflected in the forward-looking statements will be achieved or occur. Moreover, neither we nor any other person assumes responsibility for the accuracy and completeness of the forward-looking statements. We undertake no obligation to update publicly any forward-looking statements for any reason after the date of this Annual Report on Form 10-K to conform these statements to actual results or to changes in our expectations, except as required by law.   Our investor relations Web site is located at https://investors.a10networks.com. We intend to use our investor relations Web site as a means of disclosing material non-public information and for complying with our disclosure obligations under Regulation FD. Accordingly, investors should monitor this portion of our Web site, in addition to following press releases, Securities and Exchange Commission, or SEC, filings and public conference calls and webcasts. We also make available, free of charge, on our investor relations Web site under “SEC Filings,” our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to these reports as soon as reasonably practicable after electronically filing or furnishing those reports to the SEC. 3 Item 1. Business Overview PART I We are a l eading provider of secure application solutions and services that enable a new generation of intelligently connected companies with the ability to continuously improve cyber protection and digital responsiveness across dynamic Information Technology (“IT”) and network infrastructures. Our portfolio of software and hardware solutions combines industry-leading performance and scale with advanced intelligent automation, machine learning, data driven analytics, and threat intelligence to ensure security and availability of customer applications across their multi-cloud and mobile infrastructure networks, including on- premise, private and public clouds. As the cyber threat landscape intensifies and network architectures evolve, we are committed to providing customers with greater connected intelligence to improve the security, visibility, automation, availability, flexibility, management and performance of their applications. Our customers include leading cloud providers, web-scale businesses, service providers, government organizations, and enterprises. Industry Trends & Market Drivers The digitization of business has made applications a critical ingredient in virtually every aspect of operations. How safely and efficiently applications perform determines how businesses perform, how they compete, grow, and stand out in the marketplace. The application networking and security industry is experiencing dynamic shifts in the way applications are developed, delivered, monetized and protected. Our corporate strategy and technology address these evolving needs of our customers and industry, including: Increased Adoption of Cloud Applications . For decades, businesses operated with applications based in physical, appliance-based data centers. While these traditional applications remain central to businesses around the world, a new genre of cloud-based applications is emerging, presenting new opportunities and challenges that require organizations to reassess the visibility, performance and security of their applications. Some of these challenges relate to how a business effectively manages secure application services across various data centers and cloud types - whether private, public or hybrid clouds. Over time, more and more applications may be born in the cloud, while some applications that existed in traditional data centers may migrate to clouds as well. To address this shift, businesses will need solutions that bridge both traditional and cloud-based application environments and centrally manage all secure application services holistically in this multi-cloud world. Increased Network Complexity and New Infrastructure Paradigms. Traditional IT vendors may need to shift from hardware-centric models to software- defined approaches to improve agility for critical applications, and subsequently, their business operations. Ensuring product portfolios adapt and diversify to include newer virtualized software, container based software and cloud-based offerings are key factors determining future market leadership and competitive landscapes. Growing Importance of Automation and Orchestration. As applications increasingly move to a multi-cloud environment, the deployment of orchestration and automation tools has become essential to efficiently automating the deployment and operations of security and application services. There is a need for increased operational efficiency and agility, improved detection and reporting of security anomalies, enhanced end-user experiences and reduced total cost of ownership (“TCO”), simplified management of distributed application services, improved capacity planning and optimized multi-cloud software lifecycle management. By deploying newly developed secure application delivery automation and predictive analytics tools, enterprises are able to visualize their application performance, detect anomalous trends and fully automate their application delivery and network security. The Rise of DDoS Attacks. The cyberthreat landscape continues to intensify and grow. Malicious actors and cybercriminals such as hacktivists, amateur hackers, and foreign military and intelligence organizations target data centers of every type. Distributed Denial of Service (“DDoS”) attacks are increasing in size, frequency, complexity and notoriety. IT defenders are faced with the increasing sophistication of adversaries who are responsible for the size and frequency of these attacks. A DDoS attack seeks to render a target network or website unavailable by orchestrating coordinated attacks from massive worldwide networks of compromised endpoints, called botnets. Compromised endpoints can be computing 4 devices or “Internet of Things” driven devices like video cameras. Any internet-connected device can be vulnerable to hackers and utilized as part of a botnet. Rapid growth of TLS/SSL, Encrypted Applications, and Hidden Threats . Many applications use Transport Layer Security (TLS) and Secure Sockets Layer (“SSL”) protocols. Cyber criminals exploit the protocol to hide malicious malware within encrypted channels and carry out attacks against businesses and users. This malicious trend drives demand for greater visibility within SSL-encrypted channels. Businesses need a way to decrypt traffic and apply outbound security policies efficiently, and require an effective way to inspect, identify, and remediate malicious traffic, then re-encrypt traffic and deliver it quickly to its destination. Conducting this process efficiently without placing a “security performance tax” on the user experience is a critical requirement. The Advent of 5G Networks and a Smart World . The growing deployment of commercial 5G networks will bring massive increases in network throughput and significant new business opportunities for mobile carriers. It will also require a new generation of security infrastructure capable of handling the growing capacity requirements and complex management needs of 5G networks. Capacity requirements increase dramatically in 5G networks due to substantial increases in concurrent sessions, lower packet size and higher connections per second. Operators must dramatically lower latency, reduce total cost of ownership, and improve efficiency which may require advanced consolidation of network functions at the core. Meanwhile, the scope and size of DDoS attacks may also increase dramatically with the proliferation of connected devices and traffic, due in large part to the expansion of IoT/Machine-to-Machine traffic coming from new 5G-delivered Smart World applications. To address these requirements, mobile operators will need new solutions that provide hyperscale and increased performance, richer feature sets, and rich automation, analytics and threat intelligence. Need for Advanced Multi-Cloud Secure Application Service Solutions. To address these challenges, advanced and integrated solutions for managing secure application services across businesses’ application environments are needed. Of the many solution requirements, some of the more critical include: • • • • Ability to Centrally Manage Traditional and Cloud Environments. As more applications are born in the cloud, and they operate alongside traditional applications supported by on-premise and appliance-based data centers, application delivery and security solutions will be called upon to span traditional and cloud-based environments. In doing so, solutions must centrally control and manage secure application services across any combination of traditional data centers and a myriad of different clouds. To support data centers and different cloud types, solutions require a variety of form factors; hardware, software (i.e. virtual, bare metal and containers) and cloud-based offerings. Clear Visibility and Sophisticated Analytics. The effectiveness of application performance and security depends greatly on the level of visibility a business has into its application traffic. That visibility must be able to span any number of data centers and cloud types to ensure a holistic view of security threats and performance issues affecting applications. The deeper and clearer the visibility, the better the analytics and actionable information that can be applied to enhancing application performance and protection. Secure application service solutions must be driven by solid visibility and per-app analytics. Ability to Scale. Performance and security at scale are paramount in today’s dynamic application environments. Solutions need to analyze application traffic quickly and enhance performance and security in traditional and cloud-based application environments in a centrally managed manner. With the rapid adoption of IoT devices, and the advent of 5G, we believe scale will become imperative. Sophisticated Security Functionality. Secure application service solutions must detect and mitigate sophisticated cybersecurity threats, such as malicious threats hiding in encrypted traffic and DDoS attacks. To defend against the rising volume of sophisticated cyber-attacks, solutions require exceptional performance and scale without dramatically increasing footprint and total cost of ownership. Product Portfolio Our product portfolio seeks to address many of the aforementioned challenges and solution requirements. The portfolio consists of six secure application solutions and two intelligent management and automation tools. 5 Our software solutions are available to be delivered in a variety of form factors, such as embedded in optimized hardware appliances, as bare metal software, containerized software, virtual appliances and cloud-native software. While our revenue to date has predominantly derived from delivery of our proprietary software, on a perpetual license basis, embedded in optimized hardware, this model has begun to evolve in various ways, including, among others, term licenses, subscriptions, and software-only models. Our comprehensive and flexible application solutions portfolio, combined with our Harmony Controller positions the Company to address the growing need for shifting workloads to a mix of private clouds and public clouds. A10 Harmony Controller is built on microservices and container technologies and offers a multi-tenant, highly scalable controller architecture that incorporates real-time and predictive analytics at a per-app level and central management and orchestration of secure application services across hybrid environments - from physical data centers to public, private and hybrid clouds.  The following is an overview of our portfolio: Secure application solutions: 1.  2.  3.  4.  5.  6.  Thunder Application Delivery Controller (“ADC”) Lightning Application Delivery Controller (“Lightning ADC”) Thunder Carrier Grade Networking (“CGN”) Thunder Threat Protection System (“TPS”) Thunder SSL Insight (“SSLi”) Thunder Convergent Firewall (“CFW”) Intelligent management and automation tools: 1.  2.  Harmony Controller aGalaxy TPS The following is a further overview of our portfolio: Secure Application Solutions 1. Thunder Application Delivery Controller. Thunder ADC provides advanced server load balancing, including global server load balancing, high availability, aFleX scripting, aVCS, ADP multi-tenancy, SSL, offload, acceleration, caching and compression, web application firewall (“WAF”), domain name server (“DNS”) application firewall (“DAF”) and others. ADCs are typically deployed in front of a server farm within a data center, including web, application and database servers. 2. Lightning Application Delivery Controller. Lightning ADC services ADC functionality in the cloud, increasing the agility and reducing costs for customers. Introduced after the acquisition of Appcito, Inc. (“Appcito”) in 2016, Lightning ADC is a cloud-native software-as-a-service (“SaaS”) platform designed to boost the delivery and security of applications and microservices across public, private and hybrid clouds, enabling ADC-as-a-service. Central to the Lightning ADC is the SaaS-based A10 Harmony Controller, which provides central management, policy configuration, and a big data repository and analytics engine. 3. Thunder Carrier Grade Networking . Thunder CGN extends the life of increasingly scarce IPv4 address blocks and their associated infrastructure using Carrier-Grade network address translation (“CGNAT”), and also provides translation solutions to the IPv6 addressing standard. Our CGN solution is typically deployed in service provider networks to provide standards-compliant address and protocol translation services between varying types of IP addresses, and has been successfully implemented by many large service providers around the world. 4. Thunder Threat Protection System . Thunder TPS solution provides high-volume, large-scale protection for customers’ networks and server resources against massive DDoS attacks. TPS is typically deployed at the perimeter of the networks to protect internal network resources from large- scale, volumetric and multi-vector attacks. In 2017, we enhanced the TPS solution with the launch of a dedicated detector function, improved workflow and automation in aGalaxy TPS. In 2018 we enhanced our TPS detection capabilities with the One-DDoS solution, which enables Thunder ADC, CGN, and CFW solutions to act as in-line detectors, to enhance application and infrastructure detection. We also added TPS Dynamic Attack Pattern Recognition (DAPR) for 6 automatic attack learning, to identify and thwart zero-day attacks, and enhanced machine learning (ML) with always-on adaptive learning. TPS is augmented by the A10 Threat Intelligence Service which can block known bad connections (i.e., IP addresses) from entering protected networks. This service is based on software licensed from ThreatSTOP, Inc. and A10 threat research. 5. Thunder SSL Insight. Thunder SSLi eliminates the inherent blind spots created by SSL encryption by offloading CPU-intensive SSL decryption functions that enable security devices to inspect and remove malware within encrypted traffic. Thunder SSLi decrypts SSL-encrypted traffic and forwards it to a third-party security device, such as a firewall, for deep packet inspection (“DPI”). Once the traffic has been analyzed and scrubbed, Thunder SSLi re-encrypts the traffic and forwards it to its intended destination. 6. Thunder Convergent Firewall. Thunder CFW addresses multiple critical security capabilities in one package by consolidating multiple security and networking functions in a single appliance, helping customers significantly lower capital and operating expenses. Its performance and scale deliver superior value to customers, all within a small form factor, and streamlines customer operations with a cloud-ready programmable platform. Thunder CFW includes: • • • • A high-performance Secure Web Gateway with integrated explicit proxy, URL filtering and SSL visibility, enabling security policy enforcement for outbound HTTP/HTTPS client traffic. Our solution includes an Office 365 proxy to provide scalability, performance, and security to overcome deployment and operational challenges. A high-performance data center firewall with integrated network denial-of-service protection and server load balancing, and provides a Layer 4 stateful firewall and Layer 7 application-level gateway functionality for protecting data center applications from emerging network and DDoS threats. A high-performance Gi/SGi firewall with integrated network DDoS, CGNAT, ADC and application visibility. The Gi/SGi firewall protects the mobile operator infrastructures from Internet-based DDoS and other security threats. A high-performance IPsec site-to-site VPN that helps businesses secure application traffic between data centers and enables customers to securely transport application traffic over public networks. Intelligent Management and Automation Tools 1. Harmony Controller. Harmony Controller provides intelligent management, automation and analytics for secure application delivery in multi-cloud environments. Our Harmony Controller simplifies operations. Infrastructure and application operations teams can centrally manage and automate configuration and application policies for our Thunder and Lightning application and security services, such as load balancing, application delivery, web application firewall, SSL decryption, Gi/SGi firewall, Carrier Grade NAT and Office 365 solutions. Configuration and control can also be automated via application program interface (“API”) and integrated with orchestration systems used within organizations. In addition, the controller provides comprehensive infrastructure and per-application metrics and analytics for performance and security monitoring, anomaly detection and faster troubleshooting. The container-based, microservices architecture allows controller capacity to be scaled without interrupting operations. Our Harmony Controller is available in two deployment models: A10 managed software as a service (“SaaS”), or as a self-managed, on premise deployment. 2. aGalaxy TPS. a Galaxy TPS multi-device network management solution enables a network administrator to manage multiple Thunder TPS devices. aGalaxy TPS is designed to provide lower operational costs, as staff are freed up from repetitive tasks, while also increasing precision and accuracy with centralized and automated tasks, reducing the potential for human error. aGalaxy TPS is available as a hardware appliance or a software-only virtual machine. aGalaxy TPS highlights included advanced workflow and automated defense capabilities. Product Form Factors Our products are offered in a variety of form factors and payment models, including physical appliances and perpetual and subscription based software licenses, as well as pay-as-you-go licensing models and FlexPool, a flexible consumption- 7 based software model. FlexPool, allows businesses to flexibly allocate and re-distribute capacity across applications, multiple clouds and data centers. Thunder Series . ADC, CGN, TPS, SSLi, and CFW products are available on the Thunder Series family of physical appliances. The Thunder Series products support throughput ranges from 200 Mbps to 300 Gbps. The appliance family provides a variety of other security and performance options. vThunder virtual appliances operate on all major hypervisor platforms, including VMware, Microsoft Hyper-V and Linux KVM. vThunder is also available from cloud providers like Amazon Web Services (“AWS”), Microsoft Azure, and service providers. The vThunder Series products support throughput ranges from 200 Mbps to 100 Gbps. Thunder for Bare Metal is a software version of our ADC and CGN solutions that is designed to run on a variety of Intel x86 servers, allowing the customer to design and select their own hardware platform. Lightning is a cloud-native SaaS ADC product designed to boost the delivery and security of applications and microservices across public, private and hybrid clouds. Our Lightning ADC and the A10 Harmony Controller’s multi-cloud management capabilities allow flexible application deployment across multiple clouds with the ability to maintain and manage diverse workloads. Our Lightning ADC will run natively on public cloud environments, such as Amazon Web Services, Microsoft Azure, and Google Cloud Platforms. AX Series : Our ADC and CGN solutions are available on select older models from the AX Series line. Underlying Technology Since our inception, our solutions have been known for their high performance and scalability in some of the largest and most demanding networks. The value and significance of our high-performance offerings reside in our portfolio’s underlying software operating system. With the exception of Lightning ADC, our products are built on the Advanced Core Operating System (“ACOS”) platform and leverage its performance optimization and security features. The ACOS platform is optimized for modern 64-bit central processing units (“CPUs”), which increasingly have multiple parallel processing cores that operate within a single CPU for higher efficiency and performance scalability. To maximize the capabilities of these increasingly dense multi-core CPUs, ACOS implements a proprietary shared memory architecture that provides all cores with simultaneous access to common memory. This shared memory software architecture enables our products to utilize these multi-core CPUs efficiently and scale performance with increasing CPU cores. As a result, ACOS provides customers with products that can deliver superior price performance benefits over products that lack these capabilities. ACOS’ high-performance design enables our products to address a wide range of performance-driven networking challenges. The flexible software design of ACOS allows us to apply our portfolio to a variety of markets for a variety of needs. Some notable details about ACOS include: High Performance and Intelligent Network I/O Processing. In order to maximize the efficiency of high density, multi-core processors, we have developed a high performance intelligent network I/O technology that can balance application traffic flows equitably across processor cores. Our Flexible Traffic Accelerator logic can be implemented either as software running within a standard x86 processor or a Field Programmable Gate Array (“FPGA”) semiconductor. Our Flexible Traffic Accelerator (“FTA”) also performs certain hardware-based security checks for each packet and can discard suspicious traffic before it can impact system performance. Scalable and Efficient Memory Usage. To improve the performance of the multi-core processor architecture, we have developed a shared memory technology to allow all processors to share common memory and the state of the system simultaneously. This avoids the overhead associated with Inter- Processor Communication architectures deployed in first-generation approaches. We optimize memory to be visible to all cores simultaneously, while minimizing communication overhead and contention among processors for allocated memory space. All processors share a common memory pool, which dynamically allocates memory space based on application processing requirements without constraints. Customers can achieve greater performance and scalability from memory and processor resources because configurations, policies and network databases are efficiently stored within a shared memory architecture. 8 Optimized Application Networking and Security. Once data is processed and placed into a shared memory, a processor can begin to apply ACOS common services and function-specific logic. To ensure that every processor is utilized to perform every function and thereby achieve greater system utilization, ACOS uses all processor cores symmetrically for all functions and services. The ACOS common services perform a set of key operational functions, including configuration management, network I/O, aFleX scripting, Virtual Chassis System(“aVCS”), aXAPI for management integration, Application Delivery Partitions (“ADPs”), virtualization to enable multi-tenancy, and common resource management such as buffer, system memory, timer management and other internal system management tasks. ACOS features a modular software design, which improves reliability by ensuring that modifications made to one module will not have unwanted side effects on other system functions. Other noteworthy ACOS Technologies . ACOS incorporates a number of other technologies to provide a rich environment for developing Layer 4-7 application networking solutions, including: • • • • aFleX Scripting. aFleX scripting technology is based on industry-standard tool command language and enables customers to write custom scripts to augment the application processing. ADP. ADP enables multi-tenancy in the ACOS common services so that multiple departments of an organization or multiple customers can share a physical/virtual appliance. aVCS. aVCS enables multiple physical/virtual appliances to be managed as a single chassis. aXAPI . aXAPI is an industry standard representational state transfer (“RESTful”) program interface to enable management integration for automated management. Support & Services One of our founding principles is to provide excellent customer support. Our global support team is part of our engineering organization and is trained across all products and solutions, and takes complete ownership of customer issues from the beginning to the end to achieve rapid response and resolution. Our consistent, high-quality customer service and technical support is a key factor in attracting and retaining customers of all sizes, as well as support services that include installation, phone support, repair and replacement, software updates, online tools, consulting and training services. All customers receive standard warranty support for 90 days with the purchase of our products. We offer four maintenance options - Basic, Basic Plus, Gold and Platinum support programs (Platinum available in select countries). Maintenance contracts may be purchased in 12 -month increments up to five years. The average maintenance contract term is approximately 18 months. We invoice channel partners or customers directly for maintenance contracts at the time of hardware purchase, and all maintenance contracts are non-cancellable and are generally renewed through the same channel as originally purchased. Software updates are provided to all customers with a current maintenance contract on a when-and-if-available basis. We maintain technical support centers in the United States, Japan, China, India and the Netherlands. Thunder TPS features an enhanced support offering that includes access to the A10 DDoS Security Incident Response Team (“SIRT”). Augmenting the standard support, the offering includes access to a dedicated team of DDoS mitigation experts specializing in DDoS prevention, offering immediate assistance for mitigating attacks, and a subscription to the A10 Threat Intelligence Service, leveraging collective intelligence to block known threats. Our professional services team provides a full range of fee-based consulting services, including pre-sale network assessment, comprehensive network analysis and capacity planning, post-sale migration and implementation services, on-site installation and ongoing support. Customers Our customers operate in a variety of industries, including telecommunications, technology, industrial, government, retail, financial, gaming, and education. As of December 31, 2018 , we had sold our products to more than 6,000 end customers across 117 countries. Our customers include the top four United States wireless carriers, seven of the top 10 United States cable providers, and the top four service providers in Japan, in addition to other global enterprises, web giants, gaming companies and governmental organizations. During the years ended December 31, 2018 , 2017 and 2016 , purchases from our 10 largest end- customers accounted for approximately 37% , 35% and 36% of our total revenue, respectively. 9 In 2018 , two distribution channel partners, Adaptive Integration and ITOCHU Techno-Solutions Corporation, accounted for 14% and 10% of our total revenue, respectively. In 2017 , no customer accounted for more than 10% of our total revenue. In 2016 , one distribution channel partner, ITOCHU Techno- Solutions Corporation, accounted for 14% of our total revenue. In 2018, we changed the way we present revenue by customer vertical. We now report three customer verticals: service providers, enterprises and web giants compared to only service providers and enterprises in prior years. We believe this new presentation will provide more transparency into our exposure to web giant revenue which was previously primarily accounted for in enterprise revenue. The revenue by vertical percentages from prior years included in this report have been revised to conform with current year presentation. Competition As security, 5G and multi-cloud trends continue to gain prominence, changes in application delivery needs, cyber security threats, and the technology landscape result in evolving customer requirements to address application scalability, performance, security and intelligent automation. These evolving demands have expanded our addressable market into DDoS protection, 5G network security (Gi-LAN protection) and multiple areas of cloud and network security, where we compete with a number of companies not included among traditional ADC vendors. The agility and flexibility of the ACOS platform enables us to rapidly innovate and deploy solutions into adjacent markets to ADC. We have also enhanced our portfolio with the Harmony Controller, an intelligent management, automation, and predictive analytics platform for secure application delivery in multi-cloud environments and advanced protection of the 4G/5G mobile infrastructure services. This container and microservices-based product complement our comprehensive set of hardware, software and cloud offerings. We do not consider any of these markets to include a single dominant company, nor do we consider the markets to be fragmented. Our main competitors fall into the following categories: • Companies that sell products in the traditional ADC market, such as F5 Networks, Inc. (“F5 Networks”) and Citrix Systems, Inc. (“Citrix Systems”); • Companies that sell open source, software-only, cloud-based ADC services, such as Avi Networks Inc. (“Avi Networks”), NGINX Inc. (“NGiNX”), and HAProxy Technologies, Inc. (“HAProxy”) as well as many startups; • Companies that sell Gi/SGi firewall and CGN products, which were originally designed for other networking purposes, such as edge routers and security appliances from vendors like Cisco Systems, Inc. (“Cisco Systems”), Juniper Networks, Inc. (“Juniper Networks”) and Fortinet, Inc. (“Fortinet”); • Companies that sell traditional DDoS protection products, such as Arbor Networks, Inc., a subsidiary of NetScout Systems, (“Arbor Networks”) and Radware, Ltd. (“Radware”); • Companies that sell SSL decryption and inspection products, such as Symantec Corporation (through its acquisition of Blue Coat Systems Inc. in 2016) and F5 Networks; and • Companies that sell certain network security products, including Secure Web Gateways, SSL Insight/SSL Intercept, data center firewalls and Office 365 proxy solutions. The key competitive factors in our markets include: • Ability to innovate and respond to customer needs rapidly; • Ability to address on-premise and cloud application environments in a secure, centrally managed manner; • Ability to accommodate any IT delivery model or combination of models, regardless of form factor; • Breadth and depth of product features and functionality; • Level of customer satisfaction; • Price, performance, and efficiency; • Ability for products to scale with high-speed network traffic; • Flexible and agile design of products; 10 • Ability to detect and mitigate large-scale cyber security threats; • Brand awareness and reputation; • Strength of sales and marketing; and • Ability to attract and retain talented employees. Sales and Marketing Sales Our high-touch salesforce engages customers directly and through distribution channels. Our sales team is comprised of inside sales and field sales personnel who are organized by geography and maintain sales presence in 27 countries as of December 31, 2018, including in the following countries and regions: United States, Western Europe, the Middle East, Japan, China, Taiwan, South Korea, Southeast Asia and Latin America. Our sales organization includes sales engineers with deep technical domain expertise who are responsible for pre-sales technical support, solutions engineering, proof-of-concept work and technical training for our distribution channel partners. Our sales team is also comprised of a channel sales organization that is expanding our market reach through partners. We may continue to grow our sales headcount, including in geographies where we currently do not have a sales presence. Some customer sales are originated and completed by our OEM and distribution channel partners with little or no direct engagement with our sales personnel. We fulfill nearly all orders globally through our distribution channel partners, which include distributors, value added resellers and system integrators. Revenue fulfilled through our distribution channel partners accounted for 93% , 86% and 85% of our total revenue for the years ended December 31, 2018 , 2017 and 2016 , respectively. Marketing Our strategy is focused on driving greater demand for our products and services, and enabling sales to win as that demand broadens. Our marketing drives global demand generation campaigns, as well as additional awareness and demand via joint marketing campaigns with channel partners and strategic alliance partners worldwide. Our marketing also drives global awareness through industry analyst engagement, financial analyst engagement, media outreach, blogs, social media and events. Manufacturing We outsource the manufacturing of our hardware products to original design manufacturers. This approach allows us to benefit from the scale and experience of our manufacturing partners to reduce our costs, overhead and inventory while allowing us to adjust more quickly to changing customer demand. Our manufacturers are Lanner Electronics Inc. (“Lanner”), AEWIN Technologies Co., Ltd. (“AEWIN”) and iBase. These companies manufacture and assemble our hardware products using design specifications, quality assurance programs and standards established by us. Our manufacturers procure components and assemble our products based on our demand forecasts and purchase orders. These forecasts represent our estimates of future demand for our products based on historical trends and analysis from our sales and product management functions as adjusted for overall market conditions. The component parts incorporated into our products are sourced either by our manufacturing partners or directly by us. We have agreements with Lanner with an initial term of one year and AEWIN with an initial term of six years pursuant to which they manufacture, assemble, and test our products. Each agreement automatically renews for successive one-year terms unless either party gives notice that they do not want to renew. We do not have any long-term manufacturing contracts that guarantee fixed capacity or pricing. Quality assurance and testing is performed at our San Jose, Taiwan and Japan distribution centers, as well as at our manufacturers’ locations. We warehouse and deliver our products out of our San Jose warehouse for the Americas and outsource warehousing and delivery to a third-party logistics provider in some regions. 11 Backlog As of December 31, 2018 and 2017 , we had product backlog of approximately $5.9 million and $9.3 million . Backlog represents orders confirmed with a purchase order for products to be shipped generally within 90 days to customers with approved credit status. Orders are subject to cancellation, rescheduling by customers and product specification changes by customers. Although we believe that the backlog orders are firm, purchase orders may be canceled by the customer prior to shipment without significant penalty. For this reason, we believe that our product backlog at any given date is not a reliable indicator of future revenues. For the years ended December 31, 2018 , 2017 and 2016 , our total revenue was $232.2 million , $235.4 million , and $227.3 million , respectively, and our gross margin was 77.7% , 77.4% , and 76.1% , respectively. We had net losses of $27.6 million , $10.8 million and $22.4 million for the years ended December 31, 2018 , 2017 and 2016 , respectively. Intellectual Property We rely on a combination of patent, copyright, trademark and trade secret laws, and restrictions on disclosure to protect our intellectual property rights. As of December 31, 2018 , we had 140 United States (“U.S.”) patents issued and 73 U.S. patent applications pending, and 60 overseas patents issued and 25 overseas patent applications pending. Our issued U.S. patents, excluding 20 patents that we acquired, expire between 2025 and 2035 . Our issued overseas patents, excluding 11 patents that we acquired, expire between 2027 and 2037 . Our future success depends in part on our ability to protect our proprietary rights to the technologies used in our principal products. Despite our efforts to protect our proprietary rights, unauthorized parties may attempt to copy aspects of our products or to obtain and use trade secrets or other information that we regard as proprietary. In addition, the laws of some foreign countries do not protect our proprietary rights as fully as do the laws of the United States. Any issued patent may not preserve our proprietary position, and competitors or others may develop technologies similar to or superior to our technology. Our failure to enforce and protect our intellectual property rights could harm our business, operating results and financial condition. We license software from third parties for development of or integration into our products, including proprietary and open source software. We pursue registration of our trademarks and domain names in the United States and other jurisdictions. See Part I, Item 1A. Risk Factors included in this Annual Report on Form 10-K for additional information regarding the risks associated with protecting our intellectual property. Employees As of December 31, 2018 , we had 834 full-time employees, including 413 engaged in research and development and customer support, 342 in sales and marketing and 79 in general and administrative and other activities. None of our employees is represented by a labor union or is a party to any collective bargaining arrangement in connection with his or her employment with us. We have never experienced any work stoppages, and we consider our relations with our employees to be good. Corporate Information A10 Networks, Inc. was incorporated in the State of California in 2004 and subsequently reincorporated in the State of Delaware in March 2014. Our website is located at www.A10networks.com, and our investor relations website is located at http://investors.A10networks.com. The following filings are available through our investor relations website after we file them with the SEC: Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, as well as any amendments to such reports and all other filings pursuant to Section 13(a) or 15(d) of the Securities Act. These filings are also available for download free of charge on our investor relations website. Additionally, copies of materials filed by us with the SEC may be accessed at the SEC’s website at www.sec.gov. We announce material information to the public about A10, our products and services and other matters through a variety of means, including our website ( www.A10networks.com ), the investor relations section of our website ( www.investors.A10networks.com ), press releases, filings with the Securities and Exchange Commission, public conference calls, and social media, including our corporate Twitter account ( @A10Networks) and our corporate Facebook page (https://www.facebook.com/a10networks). The contents of our website and social media contents are not intended to be incorporated by reference into this Annual Report on Form 10-K or in any other report or document we file with the SEC, and any references to our websites are intended to be inactive textual references only. We encourage investors and others to review the information we make public in these locations, as such information could be deemed to be material information. Please note that this list may be updated from time to time. 12 Item 1A. Risk Factors Investing in our common stock involves a high degree of risk. You should carefully consider the risks and uncertainties described below, together with all of the other information contained in this report and in our other public filings. The risks and uncertainties described below are not the only ones we face. Additional risks and uncertainties that we are unaware of, or that we currently believe are not material, may also become important factors that affect us. If any of the following risks occur, our business, financial condition, operating results, and prospects could be materially harmed. In that event, the trading price of our common stock could decline, perhaps significantly. We have identified deficiencies in our internal control over financial reporting that resulted in material weaknesses in our internal control over financial reporting and have concluded that our internal control over financial reporting and our disclosure controls and procedures were not effective as of December 31, 2018 and December 31, 2017. If we fail to properly remediate these or any future material weaknesses or deficiencies or to maintain proper and effective internal controls, material misstatements in our financial statements could occur and impair our ability to produce accurate and timely financial statements and could adversely affect investor confidence in our financial reports, which could negatively affect our business. As described in Item 9A, “Controls and Procedures” of this report, we have concluded that our internal control over financial reporting was not effective as of December 31, 2018 and December 31, 2017, due to the existence of material weaknesses in such controls, and we have also concluded that our disclosure controls and procedures were not effective as of December 31, 2018 and December 31, 2017, due to material weaknesses in our internal control over financial reporting. While we have initiated remediation efforts to address the identified weaknesses, we cannot provide assurance that additional material weaknesses in our internal control over financial reporting will not arise or be identified in the future. We intend to continue our control remediation activities and generally improve our internal controls. In doing so, we will continue to incur expenses and expend management time on compliance-related issues. If our remediation measures are insufficient to address the identified deficiencies, or if additional deficiencies in our internal control over financial reporting are discovered or occur in the future, our consolidated financial statements may contain material misstatements and we could be required to restate our financial results. Moreover, because of the inherent limitations of any control system, material misstatements due to error or fraud may not be prevented or detected on a timely basis, or at all. If we are unable to provide reliable and timely financial reports in the future, our business and reputation may be further harmed. Restated financial statements and failures in internal controls may also cause us to fail to meet reporting obligations, negatively affect investor confidence in our management and the accuracy of our financial statements and disclosures, or result in adverse publicity and concerns from investors, any of which could have a negative effect on the price of our common stock, subject us to further regulatory investigations and penalties or stockholder litigation, and materially adversely impact our business and financial condition. The Audit Committee’s investigation of certain accounting and internal control matters relating to our previously issued financial statements and the audit of our consolidated financial statements as of and for the year ended December 31, 2017 have been time-consuming and expensive, and may result in additional expense. We have incurred significant expenses, including audit, legal, consulting and other professional fees, in connection with the Audit Committee’s internal investigation, the review of our accounting, the audit of our 2017 financial statements and the ongoing remediation of deficiencies in our internal control over financial reporting. As described in Item 9A, “Controls and Procedures,” of this report, we have taken a number of steps in order to strengthen our accounting function and attempt to reduce the risk of future recurrence and errors in accounting determinations. The validation of the efficacy of these remedial steps will result in us incurring near term expenses, and to the extent these steps are not successful, we could be required to incur significant additional time and expense. The incurrence of significant additional expense, or the requirement that management devote significant time that could reduce the time available to execute on our business strategies, could have a material adverse effect on our business, results of operations and financial condition. Our failure to timely file periodic reports we are required to file under the Securities Exchange Act of 1934 could adversely affect the market for our common stock and make it more difficult for us to access the public markets to raise debt or equity capital. We filed our Annual Report on Form 10-K for the year ended December 31, 2017 approximately five months after it was due. Because of the time required to complete and file this report, we also were unable to timely file our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2018 and June 30, 2018. 13 As a result of our inability to timely file our periodic reports under the Securities Exchange Act of 1934, we will not be eligible to use a registration statement on Form S-3 to conduct public offerings of our securities until we have timely filed all periodic reports with the SEC for a period of twelve months. Our inability to use Form S-3 during this time period may have a negative impact on our ability to access the public capital markets in a timely fashion because we would be required to file a long-form registration statement on Form S-1 and have it reviewed and declared effective by the SEC. This may limit our ability to access the public markets to raise debt or equity. If we do not successfully anticipate market needs and opportunities or if the market does not continue to adopt our application networking products, our business, financial condition and results of operations could be significantly harmed. The application networking market is rapidly evolving and difficult to predict. Technologies, customer requirements, security threats and industry standards are constantly changing. As a result, we must anticipate future market needs and opportunities and then develop new products or enhancements to our current products that are designed to address those needs and opportunities, and we may not be successful in doing so. Even if we are able to anticipate, develop and commercially introduce new products and enhancements that address the market’s needs and opportunities, there can be no assurance that new products or enhancements will achieve widespread market acceptance. For example, organizations that use other conventional or first-generation application networking products for their needs may believe that these products are sufficient. In addition, as we launch new product offerings, organizations may not believe that such new product offerings offer any additional benefits as compared to the existing application networking products that they currently use. Accordingly, organizations may continue allocating their IT budgets for existing application networking products and may not adopt our products, regardless of whether our products can offer superior performance or security. If we fail to anticipate market needs and opportunities or if the market does not continue to adopt our application networking products, then market acceptance and sales of our current and future application networking products could be substantially decreased or delayed, we could lose customers, and our revenue may not grow or may decline. Any of such events would significantly harm our business, financial condition and results of operations. Our success depends on our timely development of new products and features to address rapid technological changes and evolving customer requirements. If we are unable to timely develop and successfully introduce new products and features that adequately address these changes and requirements, our business and operating results could be adversely affected. Changes in application software technologies, data center and communications hardware, networking software and operating systems, and industry standards, as well as our end-customers’ continuing business growth, result in evolving application networking needs and requirements. Our continued success depends on our ability to identify, develop and introduce in a timely and successful manner, new products and new features for our existing products that meet these needs and requirements. Our future plans include significant investments in research and development and related product opportunities. Developing our products and related enhancements is time-consuming and expensive. We have made significant investments in our research and development team in order to address these product development needs. Our investments in research and development may not result in significant design and performance improvements or marketable products or features, or may result in products that are more expensive than anticipated. We may take longer to generate revenue, or generate less revenue, than we anticipate from our new products and product enhancements. We believe that we must continue to dedicate a significant amount of resources to our research and development efforts to maintain our competitive position. If we are unable to develop new products and features to address technological changes and new customer requirements in the application networking or security markets or if our investments in research and development do not yield the expected benefits in a timely manner, our business and operating results could be adversely affected. For example, when the 5G standards are published, we may not be able to produce a satisfactory return on investment if our strategic vision and the resources that we are spending on developing our presence in the 5G technology industry turn out to be misaligned with such standards. 14 We have experienced net losses in recent periods, anticipate increasing our operating expenses in the future and may not achieve or maintain profitability in the future. If we cannot achieve or maintain profitability, our financial performance will be harmed and our business may suffer. We experienced net losses for the years ended December 31, 2018 , 2017 and 2016 . We may not be able to increase our revenue growth or achieve profitability in the future or on a consistent basis. During the years ended December 31, 2018 , 2017 and 2016 , we have invested in our sales, marketing and research and development teams in order to develop, market and sell our products. We may continue to invest in these areas in the future. As a result of these expenditures, we may have to generate and sustain increased revenue, manage our cost structure and avoid significant liabilities to achieve future profitability. Revenue growth may slow or decline, and we may incur significant losses in the future for a number of possible reasons, including our inability to develop products that achieve market acceptance, general economic conditions, increasing competition, decreased growth in the markets in which we operate, or our failure for any reason to capitalize on growth opportunities. Additionally, we may encounter unforeseen operating expenses, difficulties, complications, delays and other unknown factors that may result in losses in future periods. If these losses exceed our expectations or our revenue growth expectations are not met in future periods, our financial performance will be harmed and our stock price could be volatile or decline. Our operating results have varied and are likely to continue to vary significantly from period to period and may be unpredictable, which could cause the trading price of our common stock to decline. Our operating results, in particular, revenue, margins and operating expenses, have fluctuated in the past, and we expect this will continue, which makes it difficult for us to predict our future operating results. The timing and size of sales of our products are highly variable and difficult to predict and can result in significant fluctuations in our revenue from period to period. This is particularly true of sales to our largest end-customers, such as service providers, Web giants and governmental organizations, who typically make large and concentrated purchases and for whom close or sales cycles can be long, as a result of their complex networks and data centers, as well as requests that may be made for customized features. Our quarterly results may vary significantly based on when these large end-customers place orders with us and the content of their orders.  Our operating results may also fluctuate due to a number of other factors, many of which are outside of our control and may be difficult to predict. In addition to other risks listed in this “Risk Factors” section, factors that may affect our operating results include: • • • • • • • • • • • • • • • fluctuations in and timing of purchases from, or loss of, large customers; the budgeting cycles and purchasing practices of end-customers; our ability to attract and retain new end-customers; changes in demand for our products and services, including seasonal variations in customer spending patterns or cyclical fluctuations in our markets; our reliance on shipments at the end of our quarters; variations in product mix or geographic locations of our sales, which can affect the revenue we realize for those sales; the timing and success of new product and service introductions by us or our competitors; our ability to increase the size of our distribution channel and to maintain relationships with important distribution channel partners; our ability to improve our overall sales productivity and successfully execute our marketing strategies; the effect of currency exchange rates on our revenue and expenses; the cost and potential outcomes of existing and future litigation; expenses related to our facility; the effect of discounts negotiated by our largest end-customers for sales or pricing pressure from our competitors; changes in the growth rate of the application networking or security markets or changes in market needs; inventory write downs, which may be necessary for our older products when our new products are launched and adopted by our end-customers; and 15 • our third-party manufacturers’ and component suppliers’ capacity to meet our product demand forecasts on a timely basis, or at all. Any one of the factors above or the cumulative effect of some of these factors may result in significant fluctuations in our financial and other operating results. This variability and unpredictability could result in our failure to meet our or our investors’ or securities analysts’ revenue, margin or other operating results expectations for a particular period, resulting in a decline in the trading price of our common stock. Reliance on shipments at the end of the quarter could cause our revenue for the applicable period to fall below expected levels. As a result of end-customer buying patterns and the efforts of our sales force and distribution channel partners to meet or exceed their sales objectives, we have historically received a substantial portion of purchase orders and generated a substantial portion of revenue during the last few weeks of each quarter. We may be able to recognize such revenue in the quarter received, however, only if all of the requirements of revenue recognition are met by the end of the quarter. Any significant interruption in our information technology systems, which manage critical functions such as order processing, revenue recognition, financial forecasts, inventory and supply chain management, could result in delayed order fulfillment and thus decreased revenue for that quarter. If expected revenue at the end of any quarter is delayed for any reason, including the failure of anticipated purchase orders to materialize (including delays by our customers or potential customers in consummating such purchase orders), our third-party manufacturers’ inability to manufacture and ship products prior to quarter-end to fulfill purchase orders received near the end of the quarter, our failure to manage inventory to meet demand, our inability to release new products on schedule, any failure of our systems related to order review and processing, or any delays in shipments or achieving specified acceptance criteria, our revenue for that quarter could fall below our, or our investors’ or securities analysts’ expectations, resulting in a decline in the trading price of our common stock. We face intense competition in our market, especially from larger, well-established companies, and we may lack sufficient financial or other resources to maintain or improve our competitive position. The application networking and security markets are intensely competitive, and we expect competition to increase in the future. To the extent that we sell our solutions in adjacent markets, we expect to face intense competition in those markets as well. We believe that our main competitors fall into the following categories: • • • • • • Companies that sell products in the traditional ADC market, such as F5 Networks, Inc. (“F5 Networks”) and Citrix Systems, Inc. (“Citrix Systems”); Companies that sell open source, software-only, cloud-based ADC services, such as Avi Networks Inc. (“Avi Networks”), NGINX Inc. (“NGiNX”), and HAProxy Technologies, Inc. (“HAProxy”) as well as many startups; Companies that sell CGN products, which were originally designed for other networking purposes, such as edge routers and security appliances from vendors like Cisco Systems, Inc. (“Cisco Systems”) Juniper Networks, Inc. (“Juniper Networks”) and Fortinet, Inc. (“Fortinet”); Companies that sell traditional DDoS protection products, such as Arbor Networks, Inc., a subsidiary of NetScout Systems, (“Arbor Networks”) and Radware, Ltd. (“Radware”): Companies that sell SSL decryption and inspection products, such as Symantec Corporation (through its acquisition of Blue Coat Systems Inc. in 2016) and F5 Networks; and Companies that sell certain network security products, including Secure Web Gateways, SSL Insight/SSL Intercept, data center firewalls and Office 365 proxy solutions. Many of our competitors are substantially larger and have greater financial, technical, research and development, sales and marketing, manufacturing, distribution and other resources and greater name recognition. In addition, some of our larger competitors have broader products offerings and could leverage their customer relationships based on their other products. Potential customers who have purchased products from our competitors in the past may also prefer to continue to purchase from these competitors rather than change to a new supplier regardless of the performance, price or features of the respective products. We could also face competition from new market entrants, which may include our current technology partners. As we continue to expand globally, we may also see new competitors in different geographic regions. Such current and potential competitors may also establish cooperative relationships among themselves or with third parties that may further enhance their resources. 16 Many of our existing and potential competitors enjoy substantial competitive advantages, such as: • • • • • • • • longer operating histories; the capacity to leverage their sales efforts and marketing expenditures across a broader portfolio of products and services at a greater range of prices, including through selling at zero or negative margins; the ability to incorporate functionality into existing products to gain business in a manner that discourages users from purchasing our products, including through product bundling or closed technology platforms; broader distribution and established relationships with distribution channel partners in a greater number of worldwide locations; access to larger end-customer bases; the ability to use their greater financial resources to attract our research and development engineers as well as other employees of ours; larger intellectual property portfolios; and the ability to bundle competitive offerings with other products and services. Our ability to compete will depend upon our ability to provide a better solution than our competitors at a competitive price. We may be required to make substantial additional investments in research and development, marketing and sales in order to respond to competition, and there is no assurance that these investments will achieve any returns for us or that we will be able to compete successfully in the future. We also expect increased competition if our market continues to expand. Moreover, conditions in our market could change rapidly and significantly as a result of technological advancements or other factors. In addition, current or potential competitors may be acquired by third parties that have greater resources available. As a result of these acquisitions, our current or potential competitors might take advantage of the greater resources of the larger organization to compete more vigorously or broadly with us. In addition, continued industry consolidation might adversely impact end-customers’ perceptions of the viability of smaller and even medium-sized networking companies and, consequently, end-customers’ willingness to purchase from companies like us. As a result, increased competition could lead to fewer end-customer orders, price reductions, reduced margins and loss of market share. Cloud-based computing trends present competitive and execution risks. We are experiencing an industry-wide trend of customers considering transitioning from purely on-premise network architectures to a computing environment that may utilize a mixture of existing solutions and various new cloud-based solutions. Concurrently with this transition, pricing and delivery models are also evolving. Many companies in our industry, including some of our competitors, are developing and deploying cloud-based solutions for their customers. In addition, the emergence of new cloud infrastructures may enable new companies to compete with our business. These new competitors may include large cloud providers who can provide their own ADC functionality as well as smaller companies targeting applications that are developed exclusively for delivery in the cloud. We are dedicating significant resources to develop and offer our customers new cloud-based solutions. Also, some of our largest customers are cloud providers that utilize our existing solutions, and we believe that as cloud infrastructures continue to grow our existing solutions may provide benefits to other cloud providers. While we believe our expertise and dedication of resources to developing new cloud-based solutions, together with the benefits that our existing solutions offer cloud providers, represent advantages that provide us with a strong foundation to compete, it is uncertain whether our efforts to develop new cloud- based solutions or our efforts to market and sell our existing solutions to cloud providers will attract the customers or generate the revenue necessary to successfully compete in this new business model. Nor is it clear when or in what manner this new business model will evolve, and this uncertainty may delay purchasing decisions by our customers or prospective customers. Whether we are able to successfully compete depends on our execution in a number of areas, including maintaining the utility, compatibility and performance of our software on the growing assortment of cloud computing platforms and the enhanced interoperability requirements associated with orchestration of cloud computing environments. Any failure to adapt to these evolving trends may reduce our revenues or operating margins and could have a material adverse effect on our business, results of operations and financial condition. 17 If we are unable to attract new end-customers, sell additional products to our existing end-customers or achieve the anticipated benefits from our investment in additional sales personnel and resources, our revenue may decline, and our gross margin will be adversely affected. To maintain and increase our revenue, we must continually add new end-customers and sell additional products to existing end-customers. The rate at which new and existing end-customers purchase solutions depends on a number of factors, including some outside of our control, such as general economic conditions. If our efforts to sell our solutions to new end-customers and additional solutions to our existing end-customers are not successful, our business and operating results will suffer. In certain recent periods, we have added personnel and other resources to our sales and marketing functions, as we focused on growing our business, entering new markets and increasing our market share. We may incur additional expenses by hiring additional sales and marketing personnel and expanding our international operations in order to seek revenue growth. The return on these and future investments may be lower, or may be realized more slowly, than we expect, if realized at all. If we do not achieve the benefits anticipated from these investments, or if the achievement of these benefits is delayed, our growth rates will decline, and our gross margin would likely be adversely affected. If we are not able to maintain and enhance our brand and reputation, our business and operating results may be harmed in tangible or intangible ways. We believe that maintaining and enhancing our brand and reputation are critical to our relationships with, and our ability to attract, new end-customers, technology partners and employees. The successful promotion of our brand will depend largely upon our ability to continue to develop, offer and maintain high- quality products and services, our marketing and public relations efforts, and our ability to differentiate our products and services successfully from those of our competitors. Our brand promotion activities may not be successful and may not yield increased revenue. In addition, extension of our brand to products and uses different from our traditional products and services may dilute our brand, particularly if we fail to maintain the quality of products and services in these new areas. We have in the past, and may in the future, become involved in litigation that could negatively affect our brand. If we do not successfully maintain and enhance our brand and reputation, our growth rate may decline, we may have reduced pricing power relative to competitors with stronger brands or reputations, and we could lose end-customers or technology partners, all of which would harm our business, operating results and financial condition. A limited number of our end-customers, including service providers, make large and concentrated purchases that comprise a significant portion of our revenue. Any loss or delay of expected purchases by our largest end-customers could adversely affect our operating results. As a result of the nature of our target market and the current stage of our development, a substantial portion of our revenue in any period comes from a limited number of large end-customers, including service providers. During the years ended December 31, 2018 , 2017 and 2016 , purchases from our ten largest end-customers accounted for approximately 37% , 35% and 36% of our total revenue, respectively. The composition of the group of these ten largest end- customers changes from period to period, but often includes service providers and web giants. During the years ended December 31, 2018 , 2017 and 2016 , service providers accounted for approximately 43% , 47% and 48% of our total revenue and web giants accounted for approximately 18% , 14% and 11% of our total revenue. Sales to these large end-customers have typically been characterized by large but irregular purchases with long initial sales cycles. After initial deployment, subsequent purchases of our products typically have a more compressed sales cycle. The timing of these purchases and of the requested delivery of the purchased product is difficult to predict. As a consequence, any acceleration or delay in anticipated product purchases by or requested deliveries to our largest end- customers could materially affect our revenue and operating results in any quarter and cause our quarterly revenue and operating results to fluctuate from quarter to quarter. We cannot provide any assurance that we will be able to sustain or increase our revenue from our largest end-customers nor that we will be able to offset any absence of significant purchases by our largest end-customers in any particular period with purchases by new or existing end-customers in that or a subsequent period. We expect that sales of our products to a limited number of end-customers will continue to contribute materially to our revenue for the foreseeable future. The loss of, or a significant delay or reduction in purchases by, a small number of end-customers could have a material adverse effect on our consolidated financial position, results of operations or cash flows. 18 Our business could be adversely impacted by changes demanded by our customers in the deployment and payment models for our products. Our customers have traditionally demanded products deployed in physical, appliance-based on-premise data centers that are paid in full at the time of purchase and include perpetual licenses for our software products. While these products remain central to our business, new deployment and payment models are emerging in our industry that may provide some of our customers with additional technical, business agility and flexibility options. These new models include cloud-based applications provided as SaaS and software subscription licenses where license and service fees are ratable and correlate to the type of service used, the quantity of services consumed or the length of time of the subscription. These models have accounting treatments that may require us to recognize revenue ratably over an extended period of time. If a substantial portion of our customers transition from on-premise-based products to such cloud-based, consumption and subscription-based models, this could adversely affect our operating results and could make it more difficult to compare our operating results during such transition period with our historical operating results. Some of our large end-customers demand favorable terms and conditions from their vendors and may request price or other concessions from us. As we seek to sell more products to these end-customers, we may agree to terms and conditions that may have an adverse effect on our business. Some of our large end-customers have significant purchasing power and, accordingly, may request from us and receive more favorable terms and conditions, including lower prices than we typically provide. As we seek to sell products to this class of end-customer, we may agree to these terms and conditions, which may include terms that reduce our gross margin and have an adverse effect on our business. Our gross margin may fluctuate from period to period based on the mix of products sold, the geographic location of our customers, price discounts offered, required inventory write downs and exchange rate fluctuations. Our gross margin may fluctuate from period to period in response to a number of factors, such as the mix of our products sold and the geographic locations of our sales. Our products tend to have varying gross margins in different geographic regions. We also may offer pricing discounts from time to time as part of a targeted sales campaign or as a result of pricing pressure from our competitors. In addition, our larger end-customers may negotiate pricing discounts in connection with large orders they place with us. The sale of our products at discounted prices could have a negative impact on our gross margin. We also must manage our inventory of existing products when we introduce new products. If we are unable to sell the remaining inventory of our older products prior to or following the launch of such new product offerings, we may be forced to write down inventory for such older products, which could also negatively affect our gross margin. Our gross margin may also vary based on international currency exchange rates. In general, our sales are denominated in U.S. dollars; however, in Japan they are denominated in Japanese yen. Changes in the exchange rate between the U.S. dollar and the Japanese yen may therefore affect our actual revenue and gross margin. We have been, may presently be, or in the future may be, a party to litigation and claims regarding intellectual property rights, resolution of which has been and may in the future be time-consuming, expensive and adverse to us, as well as require a significant amount of resources to prosecute, defend, or make our products non-infringing. Our industry is characterized by the existence of a large number of patents and by increasingly frequent claims and related litigation based on allegations of infringement or other violations of patent and other intellectual property rights. In the ordinary course of our business, we have been and may presently be in disputes and licensing discussions with others regarding their patents and other claimed intellectual property and proprietary rights. Intellectual property infringement and misappropriation lawsuits and other claims are subject to inherent uncertainties due to the complexity of the technical and legal issues involved, and we cannot be certain that we will be successful in defending ourselves against such claims or in concluding licenses on reasonable terms or at all. We may have fewer issued patents than some of our major competitors, and therefore may not be able to utilize our patent portfolio effectively to assert defenses or counterclaims in response to patent infringement claims or litigation brought against us by third parties. Further, litigation may involve patent holding companies or other adverse patent owners that have no relevant products revenue and against which our potential patents may provide little or no deterrence. In addition, many potential litigants have the capability to dedicate substantially greater resources than we can to enforce their intellectual property rights and to defend claims that may be brought against them. We expect that infringement claims may increase as the number of product types and the number of competitors in our market increases. Also, to the extent we gain greater visibility, 19 market exposure and competitive success, we face a higher risk of being the subject of intellectual property infringement claims. If we are found in the future to infringe the proprietary rights of others, or if we otherwise settle such claims, we could be compelled to pay damages or royalties and either obtain a license to those intellectual property rights or alter our products such that they no longer infringe. Any license could be very expensive to obtain or may not be available at all. Similarly, changing our products or processes to avoid infringing the rights of others may be costly, time-consuming or impractical. Alternatively, we could also become subject to an injunction or other court order that could prevent us from offering our products. Any of these claims, regardless of their merit, may be time-consuming, result in costly litigation and diversion of technical and management personnel, or require us to cease using infringing technology, develop non-infringing technology or enter into royalty or licensing agreements. Many of our commercial agreements require us to indemnify our end-customers, distributors and resellers for certain third-party intellectual property infringement actions related to our technology, which may require us to defend or otherwise become involved in such infringement claims, and we could incur liabilities in excess of the amounts we have received for the relevant products and/or services from our end-customers, distributors or resellers. These types of claims could harm our relationships with our end-customers, distributors and resellers, may deter future end-customers from purchasing our products or could expose us to litigation for these claims. Even if we are not a party to any litigation between an end-customer, distributor or reseller, on the one hand, and a third party, on the other hand, an adverse outcome in any such litigation could make it more difficult for us to defend our intellectual property rights in any subsequent litigation in which we are a named party. We may not be able to adequately protect our intellectual property, and if we are unable to do so, our competitive position could be harmed, or we could be required to incur significant expenses to enforce our rights. We rely on a combination of patent, copyright, trademark and trade secret laws, and contractual restrictions on disclosure of confidential and proprietary information, to protect our intellectual property. Despite the efforts we take to protect our intellectual property and other proprietary rights, these efforts may not be sufficient or effective at preventing their unauthorized use. In addition, effective trademark, patent, copyright and trade secret protection may not be available or cost-effective in every country in which we have rights. There may be instances where we are not able to protect intellectual property or other proprietary rights in a manner that maximizes competitive advantage. If we are unable to protect our intellectual property and other proprietary rights from unauthorized use, the value of those assets may be reduced, which could negatively impact our business. We also rely in part on confidentiality and/or assignment agreements with our technology partners, employees, consultants, advisors and others. These protections and agreements may not effectively prevent disclosure of our confidential information and may not provide an adequate remedy in the event of unauthorized disclosure. In addition, others may independently discover our trade secrets and intellectual property information we thought to be proprietary, and in these cases we would not be able to assert any trade secret rights against those parties. Despite our efforts to protect our intellectual property, unauthorized parties may attempt to copy or otherwise obtain and use our intellectual property or technology. Monitoring unauthorized use of our intellectual property is difficult and expensive. We have not made such monitoring a priority to date and will not likely make this a priority in the future. We cannot be certain that the steps we have taken or will take will prevent misappropriation of our technology, particularly in foreign countries where the laws may not protect our proprietary rights as fully as in the United States. If we fail to protect our intellectual property adequately, our competitors might gain access to our technology, and our business might be harmed. In addition, even if we protect our intellectual property, we may need to license it to competitors, which could also be harmful. For example, as a result of the settlement of an intellectual property matter, we have already licensed all of our issued patents, pending applications, and future patents and patent applications that we may acquire, obtain, apply for or have a right to license to Brocade Communications Systems, Inc. until May 2025, for the life of each such patent. In addition, we might incur significant expenses in defending our intellectual property rights. Any of our patents, copyrights, trademarks or other intellectual property rights could be challenged by others or invalidated through administrative process or litigation. We may in the future initiate claims or litigation against third parties for infringement of our proprietary rights or to establish the validity of our proprietary rights. Any litigation, whether or not resolved in our favor, could result in significant expense to us and divert the efforts of our management and technical personnel, as well as cause other claims to be made against us, which might adversely affect our business, operating results and financial condition. 20 We generate a significant amount of revenue from sales to distributors, resellers, and end-customers outside of the United States, and we are therefore subject to a number of risks that could adversely affect these international sources of our revenue. A significant portion of our revenue is generated in international markets, including Japan, Western Europe, China, Taiwan and South Korea. During the years ended December 31, 2018 , 2017 and 2016 , approximately 55% , 51% and 49% of our total revenue, respectively, was generated from customers located outside of the United States. If we are unable to maintain or continue to grow our revenue in these markets, our financial results may suffer. As a result, we must hire and train experienced personnel to staff and manage our foreign operations. To the extent that we experience difficulties in recruiting, training, managing and retaining an international staff, and specifically sales management and sales personnel, we may experience difficulties in sales productivity in foreign markets. We also seek to enter into distributor and reseller relationships with companies in certain international markets where we do not have a local presence. If we are not able to maintain successful distributor relationships internationally or recruit additional companies to enter into distributor relationships, our future success in these international markets could be limited. Business practices in the international markets that we serve may differ from those in the United States and may require us in the future to include terms in customer contracts other than our standard terms. To the extent that we may enter into customer contracts in the future that include non-standard terms, our operating results may be adversely impacted. We have a significant presence in international markets and plan to continue to expand our international operations, which exposes us to a number of risks that could affect our future growth. Our sales team is comprised of field sales and inside sales personnel who are organized by geography and maintain sales presence in 27 countries as of December 31, 2018, including in the following countries and regions: United States, Western Europe, the Middle East, Japan, China, Taiwan, South Korea, Southeast Asia and Latin America. We expect to continue to increase our sales headcount in all markets, particularly in markets where we currently do not have a sales presence. As we continue to expand our international sales and operations, we are subject to a number of risks, including the following: • • • • • greater difficulty in enforcing contracts and accounts receivable collection and possible longer collection periods; increased expenses incurred in establishing and maintaining office space and equipment for our international operations; greater difficulty in recruiting local experienced personnel, and the costs and expenses associated with such activities; general economic and political conditions in these foreign markets; economic uncertainty around the world, including continued economic uncertainty as a result of sovereign debt issues in Europe and the United Kingdom’s decision to exit the European Union (commonly referred to as “Brexit”); • management communication and integration problems resulting from cultural and geographic dispersion; • • • • • risks associated with trade restrictions and foreign legal requirements, including the importation, certification, and localization of our products required in foreign countries; greater risk of unexpected changes in regulatory practices, tariffs, and tax laws and treaties; the uncertainty of protection for intellectual property rights in some countries; greater risk of a failure of foreign employees to comply with both U.S. and foreign laws, including antitrust regulations, the U.S. Foreign Corrupt Practices Act (“FCPA”), and any trade regulations ensuring fair trade practices; and heightened risk of unfair or corrupt business practices in certain geographies and of improper or fraudulent sales arrangements that may impact financial results and result in restatements of, or irregularities in, financial statements. Because of our worldwide operations, we are also subject to risks associated with compliance with applicable anticorruption laws. One such applicable anticorruption law is the FCPA, which generally prohibits U.S. companies and their employees and intermediaries from making payments to foreign officials for the purpose of obtaining or keeping business, securing an advantage, or directing business to another, and requires public companies to maintain accurate books and records and a system of internal accounting controls. Under the FCPA, U.S. companies may be held liable for actions taken by 21 directors, officers, employees, agents, or other strategic or local partners or representatives. As such, if we or our intermediaries, such as channel partners and distributors, fail to comply with the requirements of the FCPA or similar legislation, governmental authorities in the United States and elsewhere could seek to impose civil and/or criminal fines and penalties which could have a material adverse effect on our business, operating results and financial condition. We are exposed to fluctuations in currency exchange rates, which could negatively affect our results of operations. Our consolidated results of operations, financial position and cash flows are subject to fluctuations due to changes in foreign currency exchange rates. Historically, the majority of our revenue contracts are denominated in U.S. dollars, with the most significant exception being Japan, where we invoice primarily in the Japanese yen. Our expenses are generally denominated in the currencies in which our operations are located, which is primarily in North America and EMEA. Revenue resulting from selling in local currencies and costs incurred in local currencies are exposed to foreign currency exchange rate fluctuations that can affect our operating income. The currency exchange impact of the foreign exchange rates on our net loss was $0.7 million and $0.4 million unfavorable for the years ended December 31, 2018 and 2017 , respectively. As exchange rates vary, our operating income may differ from expectations. We deploy normal and customary hedging practices that are designed to proactively mitigate such exposure. The use of such hedging activities may not offset any, or more than a portion, of the adverse financial effects of unfavorable movements in currency exchange rates over the limited time the hedges are in place and would not protect us from long term shifts in currency exchange rates. Our success depends on our key personnel and our ability to hire, retain and motivate qualified product development, sales, marketing and finance personnel. Our success depends to a significant degree upon the continued contributions of our key management, product development, sales, marketing and finance personnel, many of whom may be difficult to replace. The complexity of our products, their integration into existing networks and ongoing support of our products requires us to retain highly trained professional services, customer support and sales personnel with specific expertise related to our business. Competition for qualified professional services, customer support, engineering and sales personnel in our industry is intense, because of the limited number of people available with the necessary technical skills and understanding of our products. Our ability to recruit and hire these personnel is harmed by tightening labor markets, particularly in the engineering field, in several of our key geographic hiring areas. We may not be successful in attracting, integrating, or retaining qualified personnel to fulfill our current or future needs, nor may we be successful in keeping the qualified personnel we currently have. Our ability to hire and retain these personnel may be adversely affected by volatility or reductions in the price of our common stock, since these employees are generally granted equity-based awards. Our future performance also depends on the continued services and continuing contributions of certain employees and members of senior management to execute on our business plan and to identify and pursue new opportunities and product innovations. Our senior management team, significant employees with technical expertise, and production and sales managers, among others, are critical to the development of our technology and the future vision and strategic direction of our company. The loss of their services could significantly delay or prevent the achievement of our development and strategic objectives, which could adversely affect our business, financial condition, and operating results. Adverse general economic conditions or reduced information technology spending may adversely impact our business. A substantial portion of our business depends on the demand for information technology by large enterprises and service providers, the overall economic health of our current and prospective end-customers and the continued growth and evolution of the Internet. The timing of the purchase of our products is often discretionary and may involve a significant commitment of capital and other resources. Volatility in the global economic market or other effects of global or regional economic weakness, including limited availability of credit, a reduction in business confidence and activity, deficit-driven austerity measures that continue to affect governments and educational institutions, and other difficulties may affect one or more of the industries to which we sell our products and services. If economic conditions in the United States, Europe and other key markets for our products continue to be volatile or do not improve or those markets experience another downturn, many end-customers may delay or reduce their IT spending. This could result in reductions in sales of our products and services, longer sales cycles, slower adoption of new technologies and increased price competition. Any of these events would likely harm our business, operating results and financial condition. In addition, there can be no assurance that IT spending levels will increase following any recovery. 22 Exposure to UK political developments, including the outcome of the UK referendum on membership in the European Union, could have a material adverse effect on us. On June 23, 2016, a referendum was held on the United Kingdom’s membership in the European Union, the outcome of which was a vote in favor of leaving the European Union (commonly referred to as “Brexit”). The Brexit vote creates an uncertain political and economic environment in the United Kingdom and potentially across other European Union member states, which may last for a number of months or years. The result of the Brexit vote means that the nature of the United Kingdom’s long-term relationship with the European Union is unclear and that there is considerable uncertainty as to when any such relationship will be agreed and implemented. In the interim, there is a risk of economic instability for both the United Kingdom and the European Union, which could adversely affect our results, financial condition and prospects. The political and economic uncertainty created by the Brexit vote has caused and may continue to cause significant volatility in global financial markets and in the value of the Pound Sterling currency or other currencies, including the Euro. Depending on the terms reached regarding any exit from the European Union, it is possible that there may be adverse practical and/or operational implications on our business. Consequently, no assurance can be given as to the overall impact of the Brexit and, in particular, no assurance can be given that our operating results, financial condition and prospects would not be adversely impacted by the result. Enhanced United States tax, tariff, import/export restrictions, Chinese regulations or other trade barriers may have a negative effect on global economic conditions, financial markets and our business. There is currently significant uncertainty about the future relationship between the United States and various other countries, most significantly China, with respect trade policies, treaties, tariffs and taxes, including trade policies and tariffs regarding China. The current U.S. presidential administration has called for substantial changes to U.S. foreign trade policy with respect to China and other countries, including the possibility of imposing greater restrictions on international trade and significant increases in tariffs on goods imported into the United States. In 2018, the Office of the U.S. Trade Representative (the “USTR”) enacted tariffs on imports into the U.S. from China, including communications equipment products and components manufactured and imported from China. The tariff became effective on September 24, 2018, with an initial rate of 10% and was scheduled to increase from 10% to 25% on January 1, 2019; however, that increase has been delayed for 90 days pending trade negotiations between the U.S. and China. In addition, the tariffs may be increased in the future. It is expected that these tariffs will cause our costs to increase, which could narrow the profits we earn from sales of products requiring such materials. Furthermore, if tariffs, trade restrictions, or trade barriers are placed on products such as ours by foreign governments, especially China, the prices for our products may increase, which may result in the loss of customers and our business, financial condition and results of operations may be harmed. There can be no assurance that we will not experience a disruption in our business related to these or other changes in trade practices and the process of changing suppliers in order to mitigate any such tariff costs could be complicated, time-consuming, and costly. Furthermore, the U.S. tariffs may cause customers to delay orders as they evaluate where to take delivery of our products in connection with their efforts to mitigate their own tariff exposure. Such delays create forecasting difficulties for us and increase the risk that orders might be canceled or might never be placed. Current or future tariffs imposed by the U.S. may also negatively impact our customers' sales, thereby causing an indirect negative impact on our own sales. Any reduction in our customers' sales, and/or any apprehension among distributors and customers of a possible reduction in such sales, would likely cause an indirect negative impact on our own sales. Additionally, the current uncertainty about the future relationship between the United States and other countries with respect to the trade policies, treaties, taxes, government regulations and tariffs makes it difficult to plan for the future. New developments in these areas, or the perception that any of them could occur, may have a material adverse effect on global economic conditions and the stability of global financial markets, and may significantly reduce global trade and, in particular, trade between these nations and the United States. Any of these factors could depress economic activity and restrict our access to suppliers or customers and have a material adverse effect on our business, financial condition and results of operations and affect our strategy in China and elsewhere around the world. Given the uncertainty of further developments related to tariffs, international trade agreements and policies we can give no assurance that our business, financial condition, and operating results would not be adversely affected. 23 We are dependent on third-party manufacturers, and changes to those relationships, expected or unexpected, may result in delays or disruptions that could harm our business. We outsource the manufacturing of our hardware components to third-party original design manufacturers who assemble these hardware components to our specifications. Our primary manufacturers are Lanner and AEWIN, each of which is located in Taiwan. Our reliance on these third-party manufacturers reduces our control over the manufacturing process and exposes us to risks, including reduced control over quality assurance, product costs, and product supply and timing. Any manufacturing disruption at these manufacturers could severely impair our ability to fulfill orders. Our reliance on outsourced manufacturers also may create the potential for infringement or misappropriation of our intellectual property rights or confidential information. If we are unable to manage our relationships with these manufacturers effectively, or if these manufacturers suffer delays or disruptions for any reason, experience increased manufacturing lead- times, experience capacity constraints or quality control problems in their manufacturing operations, or fail to meet our future requirements for timely delivery, our ability to ship products to our end-customers would be severely impaired, and our business and operating results would be seriously harmed. These manufacturers typically fulfill our supply requirements on the basis of individual orders. We do not have long-term contracts with our manufacturers that guarantee capacity, the continuation of particular pricing terms, or the extension of credit limits. Accordingly, they are not obligated to continue to fulfill our supply requirements, which could result in supply shortages, and the prices we are charged for manufacturing services could be increased on short notice. In addition, our orders may represent a relatively small percentage of the overall orders received by our manufacturers from their customers. As a result, fulfilling our orders may not be considered a priority by one or more of our manufacturers in the event the manufacturer is constrained in its ability to fulfill all of its customer obligations in a timely manner. Although the services required to manufacture our hardware components may be readily available from a number of established manufacturers, it is time- consuming and costly to qualify and implement such relationships. If we are required to change manufacturers, whether due to an interruption in one of our manufacturers’ businesses, quality control problems or otherwise, or if we are required to engage additional manufacturers, our ability to meet our scheduled product deliveries to our customers could be adversely affected, which could cause the loss of sales to existing or potential customers, delayed revenue or an increase in our costs that could adversely affect our gross margin. Because some of the key components in our products come from limited sources of supply, we are susceptible to supply shortages or supply changes, which could disrupt or delay our scheduled product deliveries to our end-customers and may result in the loss of sales and end-customers. Our products incorporate key components, including certain integrated circuits that we and our third-party manufacturers purchase on our behalf from a limited number of suppliers, including some sole-source providers. In addition, the lead times associated with these and other components of our products can be lengthy and preclude rapid changes in quantities and delivery schedules. Moreover, long-term supply and maintenance obligations to our end-customers increase the duration for which specific components are required, which may further increase the risk we may incur component shortages or the cost of carrying inventory. If we are unable to obtain a sufficient quantity of these components in a timely manner for any reason, sales and/or shipments of our products could be delayed or halted, which would seriously affect present and future sales and cause damage to end-customer relationships, which would, in turn, adversely affect our business, financial condition and results of operations. In addition, our component suppliers change their selling prices frequently in response to market trends, including industry-wide increases in demand, and because we do not necessarily have contracts with these suppliers, we are susceptible to price fluctuations related to raw materials and components. If we are unable to pass component price increases along to our end-customers or maintain stable pricing, our gross margin and operating results could be negatively impacted. Furthermore, poor quality in sole-sourced components or certain other components in our products could also result in lost sales or lost sales opportunities. If the quality of such components does not meet our standards or our end-customers’ requirements, if we are unable to obtain components from our existing suppliers on commercially reasonable terms, or if any of our sole source providers cease to continue to manufacture such components or to remain in business, we could be forced to redesign our products and qualify new components from alternate suppliers. The development of alternate sources for those components can be time-consuming, difficult and costly, and we may not be able to develop alternate or second sources in a timely manner. Even if we are able to locate alternate sources of supply, we could be forced to pay for expedited shipments of such components or our products at dramatically increased costs. 24 Real or perceived defects, errors, or vulnerabilities in our products or services or the failure of our products or services to block a threat or prevent a security breach could harm our reputation and adversely impact our results of operations. Because our products and services are complex, they have contained and may contain design or manufacturing defects or errors that are not detected until after their commercial release and deployment by our customers. Even if we discover those weaknesses, we may not be able to correct them promptly, if at all. Defects may cause our products to be vulnerable to security attacks, cause them to fail to help secure networks, or temporarily interrupt end-customers’ networking traffic. Furthermore, our products may fail to detect or prevent malware, viruses, worms or similar threats for any number of reasons, including our failure to enhance and expand our platform to reflect industry trends, new technologies and new operating environments, the complexity of the environment of our end- customers and the sophistication of malware, viruses and other threats. Data thieves and hackers are increasingly sophisticated, often affiliated with organized crime or state-sponsored groups, and may operate large-scale and complex automated attacks. The techniques used to obtain unauthorized access or to sabotage networks change frequently and may not be recognized until launched against a target. Additionally, as a well-known provider of enterprise security solutions, our networks, products, and services could be targeted by attacks specifically designed to disrupt our business and harm our reputation. As our products are adopted by an increasing number of enterprises and governments, it is possible that the individuals and organizations behind advanced attacks will focus on finding ways to defeat our products. In addition, defects or errors in our updates to our products could result in a failure of our services to effectively update end-customers’ products and thereby leave our end-customers vulnerable to attacks. Our data centers and networks may experience technical failures and downtime, may fail to distribute appropriate updates, or may fail to meet the increased requirements of a growing installed end-customer base, any of which could temporarily or permanently expose our end-customers’ networks, leaving their networks unprotected against security threats. Our end-customers may also misuse or wrongly configure our products or otherwise fall prey to attacks that our products cannot protect against, which may result in loss or a breach of business data, data being inaccessible due to a “ransomware” attack, or other security incidents. For all of these reasons, we may be unable to anticipate all data security threats or provide a solution in time to protect our end-customers’ networks. If we fail to identify and respond to new and increasingly complex methods of attack and to update our products to detect or prevent such threats in time to protect our end-customers’ critical business data, our business, operating results and reputation could suffer. If any companies or governments that are publicly known to use our platform are the subject of a cyberattack that becomes publicized, our other current or potential channel partners or end-customers may look to our competitors for alternatives to our products. Real or perceived security breaches of our end- customers’ networks could cause disruption or damage to their networks or other negative consequences and could result in negative publicity to us, damage to our reputation, declining sales, increased expenses and end-customer relations issues. To the extent potential end-customers or industry analysts believe that the occurrence of any actual or perceived failure of our products to detect or prevent malware, viruses, worms or similar threats is a flaw or indicates that our products do not provide significant value, our reputation and business could be harmed. Any real or perceived defects, errors, or vulnerabilities in our products, or any failure of our products to detect a threat, could result in: • • • • • • • a loss of existing or potential end-customers or channel partners; delayed or lost revenue; a delay in attaining, or the failure to attain, market acceptance; the expenditure of significant financial and product development resources in efforts to analyze, correct, eliminate, or work around errors or defects, to address and eliminate vulnerabilities, to remediate harms potentially caused by those vulnerabilities, or to identify and ramp up production with third-party providers; an increase in warranty claims, or an increase in the cost of servicing warranty claims, either of which would adversely affect our gross margins; harm to our reputation or brand; and litigation, regulatory inquiries, or investigations that may be costly and further harm our reputation. Although we maintain cyber liability coverage that may cover certain liabilities in connection with a security breach, we cannot be certain that our insurance coverage will be adequate for liabilities actually incurred, that insurance will continue to be available to use on commercially reasonable terms, or at all, or that any insurer will not deny coverage as to any future claim. The successful assertion of one or more large claims against us that exceed available insurance coverage, or the occurrence of changes in our insurance policies, including premium increases or the imposition of large deductible or co- 25 insurance requirements, could have a material adverse effect on our business, including our financial condition, results of operation and reputation. Our business is subject to the risks of warranty claims, product returns, product liability, and product defects. Real or perceived errors, failures or bugs in our products could result in claims by end-customers for losses that they sustain. If end-customers make these types of claims, we may be required, or may choose, for customer relations or other reasons, to expend additional resources in order to help correct the problem. Historically, the amount of warranty claims has not been significant, but there are no assurances that the amount of such claims will not be material in the future. Liability provisions in our standard terms and conditions of sale, and those of our resellers and distributors, may not be enforceable under some circumstances or may not fully or effectively protect us from customer claims and related liabilities and costs, including indemnification obligations under our agreements with resellers, distributors or end-customers. The sale and support of our products also entail the risk of product liability claims. We maintain insurance to protect against certain types of claims associated with the use of our products, but our insurance coverage may not adequately cover any such claims. In addition, even claims that ultimately are unsuccessful could result in expenditures of funds in connection with litigation and divert management’s time and other resources. Failure to protect and ensure the confidentiality and security of data could lead to legal liability, adversely affect our reputation and have a material adverse effect on our operating results, business and reputation. We may collect, store and use certain confidential information in the course of providing our services, and we have invested in preserving the security of this data. We may also outsource operations to third-party service providers to whom we transmit certain confidential data. There are no assurances that any security measures we have in place, or any additional security measures that our subcontractors may have in place, will be sufficient to protect this confidential information from unauthorized security breaches. We cannot assure you that, despite the implementation of these security measures, we will not be subject to a security incident or other data breach or that this data will not be compromised. We may be required to expend significant capital and other resources to protect against security breaches or to alleviate problems caused by security breaches, or to pay penalties as a result of such breaches. Despite our implementation of security measures, techniques used to obtain unauthorized access or to sabotage systems change frequently and may not be recognized until launched against a target. As a result, we may be unable to anticipate these techniques or implement adequate preventative measures to protect this data. In addition, security breaches can also occur as a result of non- technical issues, including intentional or inadvertent breaches by our employees or service providers or by other persons or entities with whom we have commercial relationships. Any compromise or perceived compromise of our security could damage our reputation with our end-customers, and could subject us to significant liability, as well as regulatory action, including financial penalties, which would materially adversely affect our brand, results of operations, financial condition, business and prospects. We have incurred, and expect to continue to incur, significant costs to protect against security breaches. We may incur significant additional costs in the future to address problems caused by any actual or perceived security breaches. Breaches of our security measures or those of our third-party service providers, or other security incidents, could result in: unauthorized access to our sites, networks and systems; unauthorized access to, misuse or misappropriation of information, including personally identifiable information, or other confidential or proprietary information of ourselves or third parties; viruses, worms, spyware or other malware being served from our sites, networks or systems; deletion or modification of content or the display of unauthorized content on our sites; interruption, disruption or malfunction of operations; costs relating to notification of individuals, or other forms of breach remediation; deployment of additional personnel and protection technologies; response to governmental investigations and media inquiries and coverage; engagement of third-party experts and consultants; litigation, regulatory investigations, prosecutions, and other actions; and other potential liabilities. If any of these events occurs, or is believed to occur, our reputation and brand could be damaged, our business may suffer, we could be required to expend significant capital and other resources to alleviate problems caused by such actual or perceived breaches, we could be exposed to a risk of loss, litigation or regulatory action and possible liability, and our ability to operate our business, including our ability to provide maintenance and support services to our channel partners and end-customers, may be impaired. If current or prospective channel partners and end-customers believe that our systems and solutions do not provide adequate security for their businesses’ needs, our business and our financial results could be harmed. Additionally, actual, potential or anticipated attacks may cause us to incur increasing costs, including costs to deploy additional personnel and protection technologies, train employees and engage third-party experts and consultants. 26 Although we maintain privacy, data breach and network security liability insurance, we cannot be certain that our coverage will be adequate for liabilities actually incurred or that insurance will continue to be available to us on economically reasonable terms, or at all. Any actual or perceived compromise or breach of our security measures, or those of our third-party service providers, or any unauthorized access to, misuse or misappropriation of personally identifiable information, channel partners’ or end-customers information, or other information, could violate applicable laws and regulations, contractual obligations or other legal obligations and cause significant legal and financial exposure, adverse publicity and a loss of confidence in our security measures, any of which could have an material adverse effect on our business, financial condition and operating results. Our failure to adequately protect personal data could have a material adverse effect on our business. A wide variety of provincial, state, national, foreign, and international laws and regulations apply to the collection, use, retention, protection, disclosure, transfer, and other processing of personal data. These data protection and privacy-related laws and regulations are evolving and being tested in courts and may result in ever-increasing regulatory and public scrutiny and escalating levels of enforcement and sanctions. For example, the European Union has adopted a General Data Protection Regulation, or GDPR, which superseded the Data Protection Directive. This regulation, which took full effect on May 25, 2018 , has caused EU data protection requirements to be more stringent and provide for greater penalties. Noncompliance with the GDPR can trigger fines of up to €20 million or 4% of global annual revenues, whichever is higher. The United Kingdom also recently enacted legislation that substantially implements the GDPR. Additionally, California recently enacted the California Consumer Privacy Act, or CCPA, that will, among other things, require covered companies to provide new disclosures to California consumers, and afford such consumers new abilities to opt-out of certain sales of personal information, when it goes into effect on January 1, 2020. The CCPA recently was amended, and it is possible that it will be amended again before it goes into effect. We cannot yet predict the impact of the CCPA on our business or operations, but it may require us to modify our data processing practices and policies and to incur substantial costs and expenses in an effort to comply. Our failure to comply with applicable laws and regulations, or to protect such data, could result in enforcement action against us, including significant fines, imprisonment of company officials and public censure, claims for damages by end-customers and other affected persons and entities, damage to our reputation and loss of goodwill (both in relation to existing and prospective channel partners and end-customers), and other forms of injunctive or operations- limiting relief, any of which could have a material adverse effect on our operations, financial performance, and business. Evolving and changing definitions of personal data and personal information, within the European Union, the United States, and elsewhere, especially relating to classification of Internet Protocol (“IP”) addresses, machine identification, location data, biometric data and other information, may limit or inhibit our ability to operate or expand our business, including limiting strategic partnerships that may involve the sharing of data. We may be required to expend significant resources to modify our solutions and otherwise adapt to these changes, which we may be unable to do on commercially reasonable terms or at all, and our ability to develop new solutions and features could be limited. These developments could harm our business, financial condition and results of operations. Even if not subject to legal challenge, the perception of privacy concerns, whether or not valid, may harm our reputation and inhibit adoption of our products by current and prospective end-customers. If the general level of advanced cyberattacks declines, or is perceived by our current or potential customers to have declined, our business could be harmed. Our security business may be dependent on enterprises and governments recognizing that advanced cyberattacks are pervasive and are not effectively prevented by legacy security solutions. High visibility attacks on prominent companies and governments have increased market awareness of advanced cyberattacks and help to provide an impetus for enterprises and governments to devote resources to protecting against advanced cyberattacks, which may include testing, purchasing and deploying our products. If advanced cyberattacks were to decline, or enterprises or governments perceived a decline in the general level of advanced cyberattacks, our ability to attract new channel partners and end-customers and expand our offerings within existing channel partners and end-customers could be materially and adversely affected. An actual or perceived reduction in the threat landscape could increase our sales cycles and harm our business, results of operations and financial condition. 27 Undetected software or hardware errors may harm our business and results of operations. Our products may contain undetected errors or defects when first introduced or as new versions are released. We have experienced these errors or defects in the past in connection with new products and product upgrades. We expect that these errors or defects will be found from time to time in new or enhanced products after commencement of commercial distribution. These problems have in the past and may in the future cause us to incur significant warranty and repair costs, divert the attention of our engineering personnel from our product development efforts and cause significant customer relations problems. We may also be subject to liability claims for damages related to product errors or defects. While we carry insurance policies covering this type of liability, these policies may not provide sufficient protection should a claim be asserted. A material product liability claim may harm our business and results of operations. Any errors, defects or vulnerabilities in our products could result in: • • • • • • • expenditures of significant financial and product development resources in efforts to analyze, correct, eliminate or work around errors and defects or to address and eliminate vulnerabilities; loss of existing or potential end-customers or distribution channel partners; delayed or lost revenue; delay or failure to attain market acceptance; indemnification obligations under our agreements with resellers, distributors and/or end-customers; an increase in warranty claims compared with our historical experience or an increased cost of servicing warranty claims, either of which would adversely affect our gross margin; and litigation, regulatory inquiries, or investigations that may be costly and harm our reputation. Our use of open source software in our products could negatively affect our ability to sell our products and subject us to possible litigation. We incorporate open source software such as the Linux operating system kernel into our products. We have implemented a formal open source use policy, including written guidelines for use of open source software and business processes for approval of that use. We have developed and implemented our open source policies according to industry practice; however, best practices in this area are subject to change, because there is little reported case law on the interpretation of material terms of many open source licenses. We are in the process of reviewing our open source use and our compliance with open source licenses and implementing remediation and changes necessary to comply with the open source licenses related thereto. We cannot guarantee that our use of open source software has been, and will be, managed effectively for our intended business purposes and/or compliant with applicable open source licenses. We may face legal action by third parties seeking to enforce their intellectual property rights related to our use of such open source software. Failure to adequately manage open source license compliance and our use of open source software may result in unanticipated obligations regarding our products and services, such as a requirement that we license proprietary portions of our products or services on unfavorable terms, that we make available source code for modifications or derivative works we created based upon, incorporating or using open source software, that we license such modifications or derivative works under the terms of the particular open source license and/or that we redesign the affected products or services, which could result, for example, in a loss of intellectual property rights, or delay in providing our products and services. From time to time, there have been claims against companies that distribute or use third-party open source software in their products and services, asserting that the open source software or its combination with the products or services infringes third parties’ patents or copyrights, or that the companies’ distribution or use of the open source software does not comply with the terms of the applicable open source licenses. Use of certain open source software can lead to greater risks than use of warranted third-party commercial software, as open source licensors generally do not provide warranties or controls on the origin of such open source software. From time to time, there have been claims against companies that use open source software in their products, challenging the ownership of rights in such open source software. As a result, we could also be subject to suits by parties claiming ownership of rights in what we believe to be open source software and so challenging our right to use such software in our products. If any such claims were asserted against us, we could be required to incur significant legal expenses defending against such a claim. Further, if our defenses to such a claim were not successful, we could be, for example, subject to significant damages, be required to seek licenses from third parties in order to continue offering our products and services without infringing such third party’s intellectual property rights, be required to re-engineer such products and services, or be required to discontinue making available such products and services if re-engineering cannot be accomplished on a timely or successful basis. The need to engage in these or other remedies could increase our costs or otherwise adversely affect our business, operating results and financial condition. 28 Our products must interoperate with operating systems, software applications and hardware that are developed by others and if we are unable to devote the necessary resources to ensure that our products interoperate with such software and hardware, we may fail to increase, or we may lose market share and we may experience a weakening demand for our products. Our products must interoperate with our end-customers’ existing infrastructure, specifically their networks, servers, software and operating systems, which may be manufactured by a wide variety of vendors and original equipment manufacturers. As a result, when problems occur in a network, it may be difficult to identify the source of the problem. The occurrence of software or hardware problems, whether caused by our products or another vendor’s products, may result in the delay or loss of market acceptance of our products. In addition, when new or updated versions of our end-customers’ software operating systems or applications are introduced, we must sometimes develop updated versions of our software so that our products will interoperate properly. We may not accomplish these development efforts quickly, cost-effectively or at all. These development efforts require capital investment and the devotion of engineering resources. If we fail to maintain compatibility with these applications, our end-customers may not be able to adequately utilize our products, and we may, among other consequences, fail to increase, or we may lose market share and experience a weakening in demand for our products, which would adversely affect our business, operating results and financial condition. We license technology from third parties, and our inability to maintain those licenses could harm our business. Many of our products include proprietary technologies licensed from third parties. In the future, it may be necessary to renew licenses for third party technology or obtain new licenses for other technology. These third-party licenses may not be available to us on acceptable terms, if at all. As a result, we could also face delays or be unable to make changes to our products until equivalent technology can be identified, licensed or developed and integrated with our products. Such delays or an inability to make changes to our products, if it were to occur, could adversely affect our business, operating results and financial condition. The inability to obtain certain licenses to third-party technology, or litigation regarding the interpretation or enforcement of license agreements and related intellectual property issues, could have a material adverse effect on our business, operating results and financial condition. Failure to prevent excess inventories or inventory shortages could result in decreased revenue and gross margin and harm our business. We purchase products from our manufacturers outside of, and in advance of, reseller or end-customer orders, which we hold in inventory and sell. We place orders with our manufacturers based on our forecasts of our end-customers’ requirements and forecasts provided by our distribution channel partners. These forecasts are based on multiple assumptions, each of which might cause our estimates to be inaccurate, affecting our ability to provide products to our customers. There is a risk we may be unable to sell excess products ordered from our manufacturers. Inventory levels in excess of customer demand may result in obsolete inventory and inventory write-downs. The sale of excess inventory at discounted prices could impair our brand image and have an adverse effect on our financial condition and results of operations. Conversely, if we underestimate demand for our products or if our manufacturers fail to supply products we require at the time we need them, we may experience inventory shortages. Inventory shortages might delay shipments to resellers, distributors and customers and cause us to lose sales. These shortages may diminish the loyalty of our distribution channel partners or customers. The difficulty in forecasting demand also makes it difficult to estimate our future financial condition and results of operations from period to period. A failure to accurately predict the level of demand for our products could adversely affect our total revenue and net income, and we are unlikely to forecast such effects with any certainty in advance. Our sales cycles can be long and unpredictable, primarily due to the complexity of our end-customers’ networks and data centers and the length of their budget cycles. As a result, our sales and revenue are difficult to predict and may vary substantially from period to period, which may cause our operating results to fluctuate significantly. The timing of our sales is difficult to predict because of the length and unpredictability of our products’ sales cycles. A sales cycle is the period between initial contact with a prospective end-customer and any sale of our products. Our sales cycle, in particular to our large end-customers, may be lengthy due to the complexity of their networks and data centers. Because of this complexity, prospective end-customers generally consider a number of factors over an extended period of time before committing to purchase our products. End-customers often view the purchase of our products as a significant and strategic decision that can have important implications on their existing networks and data centers and, as a result, require considerable time to evaluate, test and qualify our products prior to making a purchase decision and placing an order to ensure that our products will successfully interoperate with our end-customers’ complex network and data centers. Additionally, the budgetary decisions at these entities can be lengthy and require multiple organization reviews. The length of time that end-customers 29 devote to their evaluation of our products and decision making process varies significantly. The length of our products’ sales cycles typically ranges from three to 12 months but can be longer for our large end-customers. In addition, the length of our close or sales cycle can be affected by the extent to which customized features are requested, in particular in our large deals. For all of these reasons, it is difficult to predict whether a sale will be completed or the particular fiscal period in which a sale will be completed, both of which contribute to the uncertainty of our future operating results. If our close or sales cycles lengthen, our revenue could be lower than expected, which would have an adverse impact on our operating results and could cause our stock price to decline. Our ability to sell our products is highly dependent on the quality of our support and services offerings, and our failure to offer high-quality support could have a material adverse effect on our business, revenue and results of operations. We believe that our ability to provide consistent, high quality customer service and technical support is a key factor in attracting and retaining end- customers of all sizes and is critical to the deployment of our products. When support is purchased our end-customers depend on our support organization to provide a broad range of support services, including on-site technical support, 24-hour support and shipment of replacement parts on an expedited basis. If our support organization or our distribution channel partners do not assist our end-customers in deploying our products effectively, succeed in helping our end- customers resolve post-deployment issues quickly, or provide ongoing support, it could adversely affect our ability to sell our products to existing end-customers and could harm our reputation with potential end-customers. We currently have technical support centers in the United States, Japan, China, India and the Netherlands. As we continue to expand our operations internationally, our support organization will face additional challenges, including those associated with delivering support, training and documentation in languages other than English. We typically sell our products with maintenance and support as part of the initial purchase, and a substantial portion of our support revenue comes from renewals of maintenance and support contracts. Our end-customers have no obligation to renew their maintenance and support contracts after the expiration of the initial period. If we are unable to provide high quality support, our end-customers may elect not to renew their maintenance and support contracts or to reduce the product quantity under their maintenance and support contracts, thereby reducing our future revenue from maintenance and support contracts. Our failure or the failure of our distribution channel partners to maintain high-quality support and services could have a material and adverse effect on our business, revenue and operating results. We depend on growth in markets relating to network security, management and analysis, and lack of growth or contraction in one or more of these markets could have a material adverse effect on our results of operations and financial condition. Demand for our products is linked to, among other things, growth in the size and complexity of network infrastructures and the demand for networking technologies addressing the security, management and analysis of such infrastructures. These markets are dynamic and evolving. Our future financial performance will depend in large part on continued growth in the number of organizations investing in their network infrastructure and the amount they commit to such investments. If this demand declines, our results of operations and financial condition would be materially and adversely affected. Segments of the network infrastructure industry have in the past experienced significant economic downturns. Furthermore, the market for network infrastructure may not continue to grow at historic rates, or at all. The occurrence of any of these factors in the markets relating to network security, management and analysis could materially and adversely affect our results of operations and financial condition. Because we recognize subscription revenue from our customers over the term of their agreements, downturns or upturns in sales of our subscription based offerings will not be immediately reflected in our operating results and may adversely affect revenue in the future. We recognize subscription revenue over the term of our customer agreements. As a result, most of our subscription revenue arises from agreements entered into during previous periods. A shortfall in orders for our subscription based solutions in any one period would most likely not significantly reduce our subscription revenue for that period, but could adversely affect the revenue contribution in future periods. In addition, we may be unable to quickly reduce our cost structure in response to a decrease in these orders. Accordingly, the effect of downturns in sales of our subscription based solutions will not be fully reflected in our operating results until future periods. A subscription revenue model also makes it difficult for us to rapidly increase our revenue through additional subscription sales in any one period, as revenue is generally recognized over a longer period. 30 Our business and operations have experienced growth in certain prior periods and may experience rapid growth at certain times in the future, and if we do not effectively manage any future growth or are unable to improve our controls, systems and processes, our operating results will be adversely affected. In certain prior periods, we have significantly increased the number of our employees and independent contractors. As we hire new employees and independent contractors and expand into new locations outside the United States, we are required to comply with varying local laws for each of these new locations. We anticipate that further expansion of our infrastructure and headcount will be required. Our growth has placed, and will continue to place, a significant strain on our administrative and operational infrastructure and financial resources. Our ability to manage our operations and growth across multiple countries will require us to continue to refine our operational, financial and management controls, human resource policies, and reporting systems and processes. We need to continue to improve our internal systems, processes, and controls to effectively manage our operations and growth. We may not be able to successfully implement improvements to these systems, processes and controls in an efficient or timely manner. In addition, our systems and processes may not prevent or detect all errors, omissions or fraud. For example, as described in Item 9A, “Controls and Procedures,” of this report, we identified material weaknesses in our internal control over financial reporting and concluded that our internal control over financial reporting and our disclosure controls and procedures were not effective as of December 31, 2018 and December 31, 2017. We may experience difficulties in managing improvements to our systems, processes, and controls or in connection with third-party software, which could impair our ability to provide products or services to our customers in a timely manner, causing us to lose customers, limit us to smaller deployments of our products, increase our technical support costs, or damage our reputation and brand. Furthermore, given our growth and size, our management team may lack oversight on certain side agreements between sales personnel and customers. Our failure to improve our systems and processes, or their failure to operate in the intended manner, may result in our inability to manage the growth of our business and to accurately forecast our revenue, expenses, and earnings, or to prevent certain losses, any of which may harm our business and results of operations. We may not be able to sustain or develop new distributor and reseller relationships, and a reduction or delay in sales to significant distribution channel partners could hurt our business. We sell our products and services through multiple distribution channels in the United States and internationally. We may not be able to increase our number of distributor or reseller relationships or maintain our existing relationships. Recruiting and retaining qualified distribution channel partners and training them on our technologies requires significant time and resources. These distribution channel partners may also market, sell and support products and services that are competitive with ours and may devote more resources to the marketing, sales and support of such competitive products. Our sales channel structure could subject us to lawsuits, potential liability and reputational harm if, for example, any of our distribution channel partners misrepresent the functionality of our products or services to end-customers or violate laws or our corporate policies. If we are unable to establish or maintain our sales channels or if our distribution channel partners are unable to adapt to our future sales focus and needs, our business and results of operations will be harmed. The terms of the 2016 Credit Facility and changes in the rate at which we can obtain indebtedness could restrict our operations, particularly our ability to respond to changes in our business or to take specified actions. In November 2016, we entered into a loan and security agreement (the “2016 Credit Facility”) with Silicon Valley Bank (“SVB”), as the lender. The 2016 Credit Facility contains a number of restrictive covenants that impose operating and financial restrictions on us, including restrictions on our ability to take actions that may be in our best interests. The 2016 Credit Facility requires us to satisfy specified covenants. As of the date of this filing, we had no outstanding balance under the 2016 Credit Facility and were in compliance with all facility covenants. However, we have experienced noncompliance with the covenants under the 2016 Credit Facility in connection with our late submission of quarterly financial statements and annual audited financial statements. While we view this as a one- time event, and while we were able to successfully negotiate a forbearance for such default and ultimately deliver the required financial statements, we may in the future fail to comply with the terms of the 2016 Credit Facility and be unable to negotiate a waiver or forbearance of any such defaults with our lender. If we fail to comply with these covenants in the future, SVB could elect to declare all amounts outstanding under the 2016 Credit Facility to be immediately due and payable and terminate all commitments to extend further credit. If SVB accelerates the repayment, if any, we may not have sufficient funds to repay our existing debt. If we were unable to repay those amounts, SVB could proceed against the collateral granted to it to secure such indebtedness. We have pledged substantially all of our assets, excluding our intellectual property, as collateral under the 2016 Credit Facility. The 2016 Credit Facility uses LIBOR as a reference rate for our revolving loans, such that the interest rate applicable to such loans may, at our option, be calculated based on LIBOR. LIBOR is the subject of recent national, international and other regulatory guidance and proposals for reform. The consequences of these developments cannot be entirely predicted, but if LIBOR is no longer available or if our lender has 31 increased costs due to changes in LIBOR, we may experience potential increases in interest rates on our revolving loans, which could adversely impact our interest expense, results of operations and cash flows. Our sales to governmental organizations are subject to a number of challenges and risks. We sell to governmental organization end-customers. Sales to governmental organizations are subject to a number of challenges and risks. Selling to governmental organizations can be highly competitive, expensive and time consuming, often requiring significant upfront time and expense without any assurance that these efforts will generate a sale. We have not yet received security clearance from the United States government, which prevents us from being able to sell directly for certain governmental uses. There can be no assurance that such clearance will be obtained, and failure to do so may adversely affect our operating results. Governmental organization demand and payment for our products may be impacted by public sector budgetary cycles and funding authorizations, with funding reductions or delays adversely affecting public sector demand for our products. Governmental organizations may have statutory, contractual or other legal rights to terminate contracts with our distributors and resellers for convenience or due to a default, and any such termination may adversely impact our future operating results. The U.S. federal government shutdown may negatively impact our business . The United States continues to face an uncertain political environment and substantial fiscal and economic challenges, which could affect future funding for the U.S. federal government’s discretionary and non-discretionary budgets. For 35 days ending on January 25, 2019, the U.S. federal government was partially shut down as a result of a lapse in appropriations from Congress. Additional or extended U.S. federal government shutdowns or any related under-staffing of the government departments or agencies that interact with our business could result in program cancellations, disruptions and stop work orders, limit the government’s ability to effectively progress programs and make timely payments, and affect our ability to successfully compete for new work. Additional or extended government shutdowns for any significant duration could additionally impact discretionary income among our customers or potential customers and financial markets in the U.S. Any lack of governmental support or staffing, decreases in discretionary income, financial market turbulence or other yet unknown impacts related to the foregoing could have an adverse impact on our business, financial condition and results of operations. The U.S. federal budget is expected to continue to be the subject of considerable debate, which could have significant impacts on the U.S. federal government’s spending broadly, and its spending with respect to the Company and the industries in which we operate. Failure to comply with governmental laws and regulations could harm our business. Our business is subject to regulation by various federal, state, local and foreign governmental entities, including agencies responsible for monitoring and enforcing employment and labor laws, workplace safety, product safety, environmental laws, consumer protection laws, anti-bribery laws, import/export controls, federal securities laws, and tax laws and regulations. In certain jurisdictions, these regulatory requirements may be more stringent than those in the United States. Noncompliance with applicable regulations or requirements could subject us to investigations, sanctions, mandatory product recalls, enforcement actions, disgorgement of profits, fines, damages, civil and criminal penalties or injunctions. If any governmental sanctions are imposed, or if we do not prevail in any possible civil or criminal litigation, our business, operating results, and financial condition could be materially adversely affected. In addition, responding to any action will likely result in a significant diversion of management’s attention and resources and an increase in professional fees. Enforcement actions and sanctions could harm our business, operating results and financial condition. We are subject to governmental export and import controls that could subject us to liability or impair our ability to compete in international markets. Our products are subject to U.S. export controls and may be exported outside the United States only with the required level of export license or through an export license exception because we incorporate encryption technology into our products. In addition, various countries regulate the import of certain encryption technology and have enacted laws that could limit our ability to distribute our products or our end-customers’ ability to implement our products in those countries. Changes in our products or changes in export and import regulations may create delays in the introduction of our products in international markets, prevent our end-customers with international operations from deploying our products throughout their global systems or, in some cases, prevent the export or import of our products to certain countries altogether. Any change in export or import regulations or related legislation, shift in approach to the enforcement or scope of existing regulations or change in the countries, persons or technologies targeted by such regulations, could result in decreased use of our products by, or in our decreased ability to export or sell our products to, existing or potential end-customers with international operations. Any 32 decreased use of our products or limitation on our ability to export or sell our products would likely adversely affect our business, operating results and financial condition. We discovered that trial software was inadvertently available for download by any international user and, on limited occasions, was downloaded by individuals located in a U.S. sanctioned country. We implemented corrective actions and filed a Voluntary Self Disclosure in February 2017 with the U.S. Department of Commerce and U.S. Department of Treasury regarding these technical violations. Both agencies closed their review without any fines or penalties. We are subject to various environmental laws and regulations that could impose substantial costs upon us. Our company must comply with local, state, federal, and international environmental laws and regulations in the countries in which we do business. We are also subject to laws, which restrict certain hazardous substances, including lead, used in the construction of our products, such as the European Union Restriction on the Use of Hazardous Substances in electrical and electronic equipment directive. We are also subject to the European Union Directive, known as the Waste Electrical and Electronic Equipment Directive (“WEEE Directive”), which requires producers of certain electrical and electronic equipment to properly label products, register as a WEEE producer, and provide for the collection, disposal and recycling of waste electronic products. Failure to comply with these environmental directives and other environmental laws could result in the imposition of fines and penalties, inability to sell covered products in certain countries, the loss of revenue, or subject us to third-party property damage or personal injury claims, or require us to incur investigation, remediation or engineering costs. Our operations and products will be affected by future environmental laws and regulations, but we cannot predict the ultimate impact of any such future laws and regulations at this time . Our products must conform to industry standards in order to be accepted by end-customers in our markets. Generally, our products comprise only a part of a data center. The servers, network, software and other components and systems of a data center must comply with established industry standards in order to interoperate and function efficiently together. We depend on companies that provide other components of the servers and systems in a data center to support prevailing industry standards. Often, these companies are significantly larger and more influential in driving industry standards than we are. Some industry standards may not be widely adopted or implemented uniformly, and competing standards may emerge that may be preferred by our end-customers. If larger companies do not support the same industry standards that we do, or if competing standards emerge, market acceptance of our products could be adversely affected and we may need to incur substantial costs to conform our products to such standards, which could harm our business, operating results and financial condition. We are dependent on various information technology systems, and failures of or interruptions to those systems could harm our business. Many of our business processes depend upon our information technology systems, the systems and processes of third parties, and on interfaces with the systems of third parties. If those systems fail or are interrupted, or if our ability to connect to or interact with one or more networks is interrupted, our processes may function at a diminished level or not at all. This could harm our ability to ship or support our products, and our financial results may be harmed. In addition, reconfiguring or upgrading our information technology systems or other business processes in response to changing business needs may be time-consuming and costly and is subject to risks of delay or failed deployment. To the extent this impacts our ability to react timely to specific market or business opportunities, our financial results may be harmed. Future acquisitions we may undertake may not result in the financial and strategic goals that are contemplated at the time of the transaction. We completed the acquisition of substantially all of the assets of Appcito in June 2016 and may make future acquisitions of complementary companies, products or technologies. With respect to the Appcito acquisition or any other future acquisitions we may undertake, we may find that the acquired businesses, products or technologies do not further our business strategy as expected, that we paid more than what the assets are later worth or that economic conditions change, all of which may generate future impairment charges. The Appcito acquisition or any future acquisitions may be viewed negatively by customers, financial markets or investors. There may be difficulty integrating the operations and personnel of an acquired business, and we may have difficulty retaining the key personnel of an acquired business. We may have difficulty in integrating acquired technologies or products with our existing product lines. Any integration process may require significant time and resources, and we may not be able to manage the process successfully. Our ongoing business and management’s attention may be disrupted or diverted by transition or integration issues and the complexity of managing geographically and culturally 33 diverse locations. We may have difficulty maintaining uniform standards, controls, procedures and policies across locations. We may experience significant problems or liabilities associated with product quality, technology and other matters. Our inability to successfully operate and integrate future acquisitions appropriately, effectively and in a timely manner, or to retain key personnel of any acquired business, could have a material adverse effect on our revenue, gross margin and expenses. Our ability to use our net operating loss carryforwards may be subject to limitation and may result in increased future tax liability to us. Generally, a change of more than 50% in the ownership of a corporation’s stock, by value, over a three-year period constitutes an ownership change for U.S. federal income tax purposes. An ownership change may limit a company’s ability to use its net operating loss carryforwards attributable to the period prior to such change. In the event we have undergone an ownership change under Section 382 of the Internal Revenue Code, if we earn net taxable income, our ability to use our pre-change net operating loss carryforwards to offset U.S. federal taxable income may become subject to limitations, which could potentially result in increased future tax liability to us. Changes in tax laws or regulations or adverse outcomes resulting from examination of our income or other tax returns could adversely affect our operating results and financial condition. We are subject to income taxes in the United States and various foreign jurisdictions, and our domestic and international tax liabilities will be subject to the allocation of expenses in differing jurisdictions. Our future effective tax rates could be subject to volatility or adversely affected by a number of factors, including: • • • • • • • • changes in the valuation of our deferred tax assets and liabilities; expected timing and amount of the release of tax valuation allowances; expiration of, or detrimental changes in, research and development tax credit laws; tax effects of stock-based compensation; costs related to intercompany restructurings; changes in tax laws, regulations, accounting principles or interpretations thereof; future earnings being lower than anticipated in countries where we have lower statutory tax rates and higher than anticipated earnings in countries where we have higher statutory tax rates; or examinations by US federal, state or foreign jurisdictions that disagree with interpretations of tax rules and regulations in regard to positions taken on tax filings. As our business grows, we are required to comply with increasingly complex taxation rules and practices. We are subject to tax in multiple U.S. tax jurisdictions and in foreign tax jurisdictions as we expand internationally. The development of our tax strategies requires additional expertise and may impact how we conduct our business. Our future effective tax rates could be unfavorably affected by changes in, or interpretations of, tax rules and regulations in the jurisdictions in which we do business or changes in the valuation of our deferred tax assets and liabilities. Furthermore, we provide for certain tax liabilities that involve significant judgment. We are subject to the examination of our tax returns by federal, state and foreign tax authorities, which could focus on our intercompany transfer pricing methodology as well as other matters. If our tax strategies are ineffective or we are not in compliance with domestic and international tax laws, our financial position, operating results and cash flows could be adversely affected. In addition, from time to time the United States, foreign and state governments make substantive changes to tax rules and the application of rules to companies. For example, the 2017 Tax Cut and Jobs Act (the “Tax Act”) creates a new requirement that certain income (i.e., Global Intangible Low-Taxed Income, or GILTI) earned by controlled foreign corporations (“CFCs”) must be included currently in the gross income of the CFCs’ U.S. shareholder. Additionally, the Ninth Circuit Court of Appeals, or the Court, issued an opinion in Altera Corp. v. Commissioner addressing cost-sharing regulations governing stock-based compensation. On August 7, 2018, a newly constituted panel issued an order withdrawing the July 24, 2018 opinion to allow the reconstituted panel to confer on the appeal, and the case was reargued on October 16, 2018. The Court is expected to issue a final opinion. We are monitoring this case and any impact the final opinion could have on our financial and effective tax rate. Furthermore, due to shifting economic and political conditions, tax policies or rates in various jurisdictions may be subject to significant change. 34 We are exposed to the credit risk of our distribution channel partners and end-customers, which could result in material losses and negatively impact our operating results. Most of our sales are on an open credit basis, with typical payment terms ranging from 30 to 90 days depending on local customs or conditions that exist in the sale location. If any of the distribution channel partners or end-customers responsible for a significant portion of our revenue becomes insolvent or suffers a deterioration in its financial or business condition and is unable to pay for our products, our results of operations could be harmed. The sales price of our products and subscriptions may decrease, which may reduce our gross profits and adversely impact our financial results. The sales prices for our products and subscriptions may decline for a variety of reasons, including competitive pricing pressures, discounts, a change in our mix of products and subscriptions, anticipation of the introduction of new products or subscriptions, or promotional programs. Competition continues to increase in the market segments in which we participate, and we expect competition to further increase in the future, thereby leading to increased pricing pressures. Larger competitors with more diverse product and service offerings may reduce the price of products or subscriptions that compete with ours or may bundle them with other products and subscriptions. Additionally, although we price our products and subscriptions worldwide in U.S. dollars (except in Japan), currency fluctuations in certain countries and regions may negatively impact actual prices that channel partners and end-customers are willing to pay in those countries and regions. Furthermore, we anticipate that the sales prices and gross profits for our products will decrease over product life cycles. We cannot guarantee that we will be successful in developing and introducing new offerings with enhanced functionality on a timely basis, or that our product and subscription offerings, if introduced, will enable us to maintain our prices and gross profits at levels that will allow us to achieve and maintain profitability. Our reported financial results may be adversely affected by changes in accounting principles generally accepted in the United States. Generally accepted accounting principles (“GAAP”) in the United States are subject to interpretation by the Financial Accounting Standards Board (“FASB”), the SEC and various bodies formed to promulgate and interpret appropriate accounting principles. A change in these principles or interpretations could have a significant effect on our reported financial results, and could affect the reporting of transactions completed before the announcement of a change. For example, in May 2014, the FASB issued Accounting Standards Update No. 2014-09 (Topic 606), Revenue from Contracts with Customers, which supersedes nearly all existing revenue recognition guidance under U.S. GAAP. We adopted Topic 606 effective January 1, 2018, applying the modified retrospective method to all contracts that were not completed as of January 1, 2018. This or other changes in accounting principles could adversely affect our financial results. See Note 2 of our Notes to the Consolidated Financial Statements included in Part II, Item 8 of this report regarding the effect of new accounting pronouncements on our financial statements. Any difficulties in implementing these pronouncements could cause us to fail to meet our financial reporting obligations, which could result in regulatory discipline and harm investors’ confidence in us. Concentration of ownership among our existing executive officers, a small number of stockholders, directors and their affiliates may prevent new investors from influencing significant corporate decisions. Our executive officers and directors, together with affiliated entities, own 27% of our outstanding common stock ( 45% if other holders of 5% or more of our outstanding common stock are also included) as of December 31, 2018 . Accordingly, these stockholders, acting together, have significant influence over the election of our directors, over whether matters requiring stockholder approval are approved or disapproved and over our affairs in general. The interests of these stockholders could conflict with your interests. These stockholders may also have an interest in pursuing acquisitions, divestitures, financings or other transactions that, in their judgment, could enhance their investments, even though such transactions might involve risks to you. In addition, this concentration of ownership could have the effect of delaying or preventing a liquidity event such as a merger or liquidation of our company. Certain stockholders could attempt to influence changes at the Company, which could adversely affect our operations, financial condition and the value of our common stock. Our stockholders may from time-to-time seek to acquire a controlling stake in us, engage in proxy solicitations, advance stockholder proposals or otherwise attempt to effect changes. Campaigns by stockholders to effect changes at publicly-traded companies are sometimes led by investors seeking to increase short-term stockholder value through actions such as financial restructuring, increased debt, special dividends, stock repurchases or sales of assets or the entire company. 35 Responding to proxy contests and other actions by activist stockholders can be costly and time-consuming, and could disrupt our operations and divert the attention of our board of directors and senior management from the pursuit of our business strategies. These actions could adversely affect our operations, financial condition and the value of our common stock. We may need to raise additional funds in future private or public offerings, and such funds may not be available on acceptable terms, if at all. If we do raise additional funds, existing stockholders will suffer dilution. We may need to raise additional funds in private or public offerings, and these funds may not be available to us when we need them or on acceptable terms, if at all. If we raise additional funds through further issuances of equity or convertible debt securities, you could suffer significant dilution, and any new equity securities we issue could have rights, preferences and privileges superior to those of our then-existing capital stock. The 2016 Credit Facility, as well as any debt financing secured by us in the future could involve restrictive covenants relating to our capital raising activities and other financial and operational matters that may make it more difficult for us to obtain additional capital and to pursue business opportunities. If we cannot raise additional funds when we need them, our business and prospects could fail or be materially and adversely affected. The price of our common stock has been and may continue to be volatile, and the value of your investment could decline. Technology stocks have historically experienced high levels of volatility. The trading price of our common stock has been and is likely to continue to be volatile and subject to fluctuations in response to many factors, some of which are beyond our control and may not be related to our operating performance. These fluctuations could cause you to lose all or part of your investment in our common stock. Factors that could cause fluctuations in the trading price of our common stock include the following: • • • • • • • • • • announcements of new products, services or technologies, commercial relationships, acquisitions or other events by us or our competitors; price and volume fluctuations in the overall stock market from time to time; significant volatility in the market price and trading volume of technology companies in general and of companies in our industry; fluctuations in the trading volume of our shares or the size of our public float; actual or anticipated changes or fluctuations in our results of operations; whether our results of operations meet the expectations of securities analysts or investors; actual or anticipated changes in the expectations of investors or securities analysts; litigation or investigations involving us, our industry, or both; regulatory developments in the United States, foreign countries or both; general economic conditions and trends; • major catastrophic events; • • sales of large blocks of our common stock; or departures of key personnel. In addition, if the market for technology stocks or the stock market in general experiences a loss of investor confidence, the trading price of our common stock could decline for reasons unrelated to our business, results of operations or financial condition. The trading price of our common stock might also decline in reaction to events that affect other companies in our industry even if these events do not directly affect us. In the past, following periods of volatility in the market price of a company’s securities, securities class action litigation has often been brought against that company. The price of our common stock has been highly volatile since our initial public offering (“IPO”) in March 2014. In January 2015, several substantially identical putative class action lawsuits alleging violations of securities laws were filed against us, our directors and certain of our executive officers and in June 2015, a related shareholder derivative action was filed. The consolidated securities class actions and the derivative action were settled in 2016 and dismissed in the first quarter of 2017. In March 2018, a putative class action lawsuit alleging violations of securities laws was filed against us and certain of our current and former executive officers, and in May 2018, a related shareholder derivative action was filed. In March 2018, the United States Securities and Exchange Commission began a private investigation into any securities laws violations by us or persons currently or formerly affiliated with us. Current or future securities litigation, including any related shareholder derivative litigation or investigation, could 36 result in substantial costs and divert our management’s attention and resources from our business. This could have a material adverse effect on our business, results of operations and financial condition. Sales of substantial amounts of our common stock in the public markets, or the perception that such sales might occur, could reduce the price that our common stock might otherwise attain and may dilute your voting power and your ownership interest in us. Sales of a substantial number of shares of our common stock in the public market, or the perception that such sales could occur, could adversely affect the market price of our common stock and may make it more difficult for you to sell your common stock at a time and price that you deem appropriate. As of December 31, 2018 , there were approximately 4.1 million vested and exercisable options to purchase our common stock, in addition to the 74.3 million common shares outstanding as of such date. All outstanding shares and all shares issuable upon exercise of outstanding and vested options are freely tradable, subject in some cases to volume and other restrictions of Rules 144 and 701 under the Securities Act, as well as our insider trading policy. In addition, holders of certain shares of our outstanding common stock, including an aggregate of 9.5 million shares held by funds affiliated with Summit Partners, L.P. as of December 31, 2018 are entitled to rights with respect to registration of these shares under the Securities Act pursuant to an investors’ rights agreement. If these holders of our common stock, by exercising their registration rights, sell a large number of shares, they could adversely affect the market price for our common stock. If we file a registration statement for the purposes of selling additional shares to raise capital and are required to include shares held by these holders pursuant to the exercise of their registration rights, our ability to raise capital may be impaired. Sales of substantial amounts of our common stock in the public market, or the perception that these sales could occur, could cause the market price of our common stock to decline. We are an emerging growth company, and any decision on our part to comply only with certain reduced disclosure requirements applicable to emerging growth companies could make our common stock less attractive to investors. We are an emerging growth company, and, for as long as we continue to be an emerging growth company, we may choose to take advantage of exemptions from various reporting requirements applicable to other public companies but not to “emerging growth companies,” including, but not limited to, not being required to have our independent registered public accounting firm audit our internal control over financial reporting under Section 404 of the Sarbanes- Oxley Act, reduced disclosure obligations regarding executive compensation in our periodic reports and proxy statements, and exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and stockholder approval of any golden parachute payments not previously approved. We could be an emerging growth company for up to five years following the completion of our initial public offering. We will remain an emerging growth company until the earliest of: (a) the last day of the year (i) following the fifth anniversary of the completion of the initial public offering, (ii) in which we have total annual gross revenue of at least $1.07 billion, or (iii) in which we qualify as a large accelerated filer, which means the market value of our common stock that is held by non- affiliates exceeds $700 million as of the prior June 30, or (b) the date on which we have issued more than $1.0 billion in non-convertible debt securities during the prior three-year period. We cannot predict if investors will find our common stock less attractive if we choose to rely on these exemptions. If some investors find our common stock less attractive as a result of any choices to reduce future disclosure, there may be a less active trading market for our common stock and the price of our common stock may be more volatile. Under the JOBS Act, emerging growth companies can also delay adopting new or revised accounting standards until such time as those standards apply to private companies. We have irrevocably elected not to avail ourselves of this accommodation allowing for delayed adoption of new or revised accounting standards, and, therefore, we will be subject to the same new or revised accounting standards as other public companies that are not emerging growth companies. Effective December 31, 2019, we will no longer be an “emerging growth company,” and the reduced disclosure requirements applicable to “emerging growth companies” will no longer apply, which will increase our costs as a result of compliance requirements with Section 404 of the Sarbanes-Oxley Act and increased demands on management. Effective December 31, 2019, we will lose our status as an “emerging growth company” as defined in the JOBS Act. As such, we will incur significant additional expenses that we did not previously incur in complying with the Sarbanes-Oxley Act and rules implemented by the SEC. Once we are no longer an “emerging growth company,” the cost of compliance with Section 404 will require us to incur substantial accounting expense and expend significant management time on compliance-related issues as we implement additional corporate governance practices and comply with reporting requirements. Moreover, if we or our independent registered public accounting firm deems current or future deficiencies in our internal control over financial reporting to be material weaknesses, we may be required to make prospective or retroactive changes to our financial statements, consider other areas for further attention or improvement, or be unable to obtain the required attestation in a timely 37 manner, if at all. In addition, the market price of our stock could decline and we could be subject to sanctions or investigations by the SEC or other regulatory authorities, which would require additional financial and management resources. We are obligated to implement and maintain effective internal control over financial reporting. As of December 31, 2018 and December 31, 2017, we concluded that our internal control over financial reporting and our disclosure controls and procedures were not effective. In the future, we may again not complete our analysis of our internal control over financial reporting in a timely manner, or our internal control over financial reporting may not be determined to be effective, or we may discover significant deficiencies or material weaknesses in our internal control over financial reporting, all of which may adversely affect investor confidence in our company and, as a result, the value of our common stock. We are required, pursuant to the Exchange Act, to furnish a report by management on, among other things, the effectiveness of our internal control over financial reporting for each fiscal year. This assessment will need to include disclosure of any material weaknesses identified by our management in our internal control over financial reporting. We have, in the past, experienced and are currently experiencing issues with our internal control over financial reporting. We have discovered and it is possible that we may discover in the future significant deficiencies or material weaknesses in our internal control over financial reporting. Current significant deficiencies and material weaknesses have resulted in a restatement of certain of our financial reports, as disclosed in Item 9A, “Controls and Procedures,” of our Annual Report on Form 10-K for the year ended December 31, 2017. If, in any future reporting periods, we are unable to conclude that our internal control over financial reporting is effective, or if we are required to restate our financial statements as a result of ineffective internal control over financial reporting, we could lose investor confidence in the accuracy and completeness of our financial reports, which would cause the price of our common stock to decline. We are required to disclose material changes made in our internal control and procedures on a quarterly basis. However, our independent registered public accounting firm will not be required to attest to the effectiveness of our internal control over financial reporting pursuant to Section 404 of the Sarbanes-Oxley Act until December 31, 2019, when we will no longer be an emerging growth company as defined in the JOBS Act, if we take advantage of the exemptions contained in the JOBS Act. To comply with these requirements, we may need to undertake various actions, such as implementing new internal controls and procedures and hiring accounting or internal audit staff. If securities or industry analysts do not publish research or reports about our business, or publish inaccurate or unfavorable research reports about our business, our share price and trading volume could decline . The market for our common stock, to some extent, depends on the research and reports that securities or industry analysts publish about us or our business. We do not have any control over these analysts. If one or more of the analysts who cover us should downgrade our shares or change their opinion of our shares, our share price would likely decline. If one or more of these analysts should cease coverage of our company or fail to regularly publish reports on us, we could lose visibility in the financial markets, which would cause our share price or trading volume to decline. Our charter documents and Delaware law could discourage takeover attempts and lead to management entrenchment. Our restated certificate of incorporation and bylaws contain provisions that could delay or prevent a change in control of our company. These provisions could also make it difficult for stockholders to elect directors that are not nominated by the current members of our board of directors or take other corporate actions, including effecting changes in our management. These provisions include: • • • a classified board of directors with three-year staggered terms, with declassification phasing in over a period of three years, beginning with the 2018 annual meeting of stockholders, which could delay the ability of stockholders to change the membership of a majority of our board of directors until our board of directors is completely declassified; the ability of our board of directors to issue shares of preferred stock and to determine the price and other terms of those shares, including preference and voting rights, without stockholder approval, which could be used to significantly dilute the ownership of a hostile acquirer; the exclusive right of our board of directors to elect a director to fill a vacancy created by the expansion of our board of directors or the resignation, death or removal of a director, which prevents stockholders from being able to fill vacancies on our board of directors; 38 • • • • • a prohibition on stockholder action by written consent, which forces stockholder action to be taken at an annual or special meeting of our stockholders; the requirement that a special meeting of stockholders may be called only by the chairman of our board of directors, our Chief Executive Officer, our secretary, or a majority vote of our board of directors, which could delay the ability of our stockholders to force consideration of a proposal or to take action, including the removal of directors; the requirement for the affirmative vote of holders of at least 66-2/3% of the voting power of all of the then-outstanding shares of the voting stock, voting together as a single class, to amend the provisions of our restated certificate of incorporation relating to the issuance of preferred stock and management of our business or our bylaws, which may inhibit the ability of an acquirer to effect such amendments to facilitate an unsolicited takeover attempt; the ability of our board of directors, by majority vote, to amend the bylaws, which may allow our board of directors to take additional actions to prevent an unsolicited takeover and inhibit the ability of an acquirer to amend the bylaws to facilitate an unsolicited takeover attempt; and advance notice procedures with which stockholders must comply to nominate candidates to our board of directors or not to propose matters to be acted upon at a stockholders’ meeting, which may discourage or deter a potential acquirer from conducting a solicitation of proxies to elect the acquiror’s own slate of directors or otherwise attempting to obtain control of us. In addition, as a Delaware corporation, we are subject to Section 203 of the Delaware General Corporation Law. These provisions may prohibit large stockholders, in particular those owning 15% or more of our outstanding voting stock, from merging or combining with us for a certain period of time. Our business is subject to the risks of earthquakes, fire, power outages, floods, and other catastrophic events, and to interruption by man-made problems such as acts of war and terrorism. A significant natural disaster, such as an earthquake, fire, a flood, or significant power outage could have a material adverse impact on our business, operating results, and financial condition. Our corporate headquarters are located in the San Francisco Bay Area, a region known for seismic activity. In addition, our two primary manufacturers are located in Taiwan, which is near major earthquake fault lines and subject to typhoons during certain times of the year. In the event of a major earthquake or typhoon, or other natural or man-made disaster, our manufacturers in Taiwan may face business interruptions, which may impact quality assurance, product costs, and product supply and timing. In the event our or our service providers’ information technology systems or manufacturing or logistics abilities are hindered by any of the events discussed above, shipments could be delayed, resulting in missed financial targets, such as revenue and shipment targets, and our operations could be disrupted, for the affected quarter or quarters. In addition, cyber security attacks, acts of war or terrorism, or other geo-political unrest could cause disruptions in our business or the business of our supply chain, manufacturers, logistics providers, partners, or end-customers or the economy as a whole. Any disruption in the business of our supply chain, manufacturers, logistics providers, partners or end-customers that impacts sales at the end of a quarter could have a significant adverse impact on our quarterly results. All of the aforementioned risks may be further increased if the disaster recovery plans for us and our suppliers prove to be inadequate. To the extent that any of the above should result in delays or cancellations of customer orders, or the delay in the manufacture, deployment or shipment of our products, our business, financial condition and operating results would be adversely affected. We do not intend to pay dividends for the foreseeable future. We intend to retain any earnings to finance the operation and expansion of our business, and we do not anticipate paying any cash dividends in the future. In addition, the 2016 Credit Facility currently restricts our ability to pay cash dividends while this facility remains outstanding. As a result, you may only receive a return on your investment in our common stock if the value of our common stock increases. Item 1B. Unresolved Staff Comments None. 39 Item 2. Properties Our corporate headquarters is located in San Jose, California, where we currently lease 79,803 square feet of space under a lease agreement that expires on January 31, 2020 . We also lease space for offices internationally and for sales offices in locations throughout the United States and various international locations, including, among others, China, Japan, the United Kingdom, the Netherlands, Taiwan, Korea, Singapore and India. We believe that our current facilities are adequate to meet our current needs. We intend to expand our facilities or add new facilities as we add employees and enter new geographic markets. We believe that alternative or additional space suitable for our requirements will be available as needed to accommodate ongoing operations and any such growth. We do however expect to incur additional expenses in connection with any such new or expanded facilities. Item 3. Legal Proceedings We have been and may currently be involved in various legal proceedings, the outcomes of which are not within our complete control or may not be known for prolonged periods of time. Management is required to assess the probability of loss and amount of such loss, if any, in preparing our consolidated financial statements. We evaluate the likelihood of a potential loss from legal proceedings to which we are a party. We record a liability for such claims when a loss is deemed probable and the amount can be reasonably estimated. Significant judgment may be required in the determination of both probability and whether an exposure is reasonably estimable. Our judgments are subjective based on the status of the legal proceedings, the merits of our defenses and consultation with in- house and outside legal counsel. As additional information becomes available, we reassess the potential liability related to pending claims and may revise our estimates. Due to the inherent uncertainties of the legal processes in the multiple jurisdictions in which we operate, our judgments may be materially different than the actual outcomes, which could have material adverse effects on our business, financial conditions and results of operations. Additional information with respect to this Item may be found in Note 6.  Commitments and Contingencies , in the notes to consolidated financial statements in Part II, Item 8 of this Annual Report on Form 10-K, which is incorporated by reference. Item 4. Mine Safety Disclosure Not applicable. 40 Item 5. Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities Market for Registrant’s Common Equity Our common stock has been quoted on the New York Stock Exchange (“NYSE”) under the symbol “ATEN.” PART II There were approximately 130 stockholders of record on February 28, 2019 . Because many shares of our common stock are held by brokers and other institutions on behalf of stockholders, we are unable to estimate the total number of stockholders represented by these holders of record. Company Stock Performance The following graph compares the cumulative total return on our common stock, the NASDAQ Composite Index and the Russell 1000 Index. The graph assumes $100 was invested on March 21, 2014 in our common stock and each index and all dividends were reinvested. The historic stock price performance is not necessarily indicative of future stock price performance. Issuer Purchases of Equity Securities On October 23, 2017, our board of directors authorized a share repurchase program for up to  $20.0 million  of our common stock over 12 months. No shares were repurchased under this program through its expiration in October 2018. Unregistered Sales of Equity Securities None. 41 Item 6. Selected Financial Data We have derived the consolidated statement of operations data for the years ended December 31, 2018, 2017 and 2016 and the selected consolidated balance sheet data as of December 31, 2018 and 2017 from our audited consolidated financial statements that are included in this Form 10-K. The following selected consolidated statement of operations data for the years ended December 31, 2015 and 2014 and the selected consolidated balance sheet data as of December 31, 2016, 2015 and 2014 are derived from our audited consolidated financial statements that are not included in this report. Our historical operating results are not necessarily indicative of future operating results, these selected consolidated financial data should be read in conjunction with the consolidated financial statements and accompanying notes in Part II, Item 8, and Management’s Discussion and Analysis of Financial Condition and Results of Operations in Part II, Item 7 included in this report. In addition, the amounts as of and for the year ended December 31, 2018 have been prepared based on our adoption of Accounting Standards Codification (“ASC”) No. 606, Contracts with Customers. We elected to adopt this accounting standard on a modified retrospective basis which resulted in the impact of adoption being recorded as of January 1, 2018. The amounts in all other years, other than 2018, in the tables below have been prepared on the previously outstanding guidance on revenue recognition. We have disclosed the ASC 606 adoption impact on our revenue recognition in Note 2 of the audited consolidated financial statements included in Part II, Item 8 of this report. (in thousands, except per share amounts) 2018 2017 2016 2015 2014 Consolidated Statement of Operations Data: Years Ended December 31, Revenue Cost of revenue Gross profit Loss from operations Net loss Net loss per share: basic and diluted Weighted-average shares used in computing net loss per share: basic and diluted Consolidated Balance Sheet Data: Cash, cash equivalents and marketable securities Working capital Total assets Deferred revenue (current and non-current) Total stockholders’ equity   $   $   $   $   $   $   $   $   $   $   $ $ $ $ $ $ $ $ $ $ $ $ 232,223   51,896   180,327   (27,679)   (27,617)   (0.38)   72,882   128,375   117,572   235,876   97,966   103,883   42 235,429   53,318   182,111   (10,372)   (10,751)   (0.15)   70,053   131,134   111,076   224,858   94,637   98,386   $ $ $ $ $ $ $ $ $ $ $ 227,297   54,413   172,884   (20,570)   (22,391)   (0.34)   65,701   114,347   95,285   216,733   91,617   82,752   $ $ $ $ $ $ $ $ $ $ $ 196,285   48,402   147,883   (40,309)   (41,897)   (0.67)   62,428   98,117   89,550   189,892   72,008   78,205   $ $ $ $ $ $ $ $ $ $ $ 179,507 42,937 136,570 (30,271) (35,870) (0.74) 48,682 91,905 100,656 186,980 57,220 96,565                                                                               Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations The following discussion and analysis of our financial condition and results of operations (“MD&A”) should be read in conjunction with our consolidated financial statements and related notes included elsewhere in this document. In addition to historical information, the MD&A contains forward- looking statements that involve risks and uncertainties. These forward-looking statements include, but are not limited to, those matters discussed under the heading “Forward-looking Statements.” Our actual results could differ materially from those anticipated by these forward‑looking statements due to various factors, including, but not limited to, those set forth under Item 1A. Risk Factors of this Form 10-K and elsewhere in this document. Overview We are a leading provider of secure application solutions and services that enable a new generation of intelligently connected companies with the ability to continuously improve cyber protection and digital responsiveness across dynamic Information Technology (“IT”) and network infrastructures. Our portfolio of software and hardware solutions combines industry-leading performance and scale with advanced intelligent automation, machine learning, data driven analytics, and threat intelligence to ensure security and availability of customer applications across their multi-cloud and mobile infrastructure networks, including on-premise, private and public clouds. As the cyber threat landscape intensifies and network architectures evolve, we are committed to providing customers with greater connected intelligence to improve the security, visibility, automation, availability, flexibility, management and performance of their applications. Our customers include leading cloud providers, web-scale businesses, service providers, government organizations and enterprises. Our product portfolio seeks to address many of the aforementioned challenges and solution requirements. The portfolio consists of six secure application solutions; Thunder Application Delivery Controller (“ADC”), Lightning Application Delivery Controller (“Lightning ADC”), Thunder Carrier Grade Networking (“CGN”), Thunder Threat Protection System (“TPS”), Thunder SSL Insight (“SSLi”) and Thunder Convergent Firewall (“CFW”) and intelligent management, and automation tools; Harmony Controller and aGalaxy TPS. Our products are offered in a variety of form factors and payment models, including physical appliances and perpetual and subscription based software licenses, as well as pay-as-you-go licensing models and FlexPool, a flexible consumption-based software model. We derive revenue from sales of products and related support services. Products revenue is generated primarily by sales of hardware appliances with perpetual licenses to our embedded software solutions. We also derive revenue from licenses to, or subscription services for, software-only versions of our solutions. We generate services revenue primarily from sales of maintenance and support contracts. Our customers predominantly purchase maintenance and support in conjunction with purchases of our products. In addition, we also derive revenue from the sale of professional services. We sell our products globally to service providers, enterprises and web giants that depend on data center applications and networks to generate revenue and manage operations efficiently. In 2018, we changed the way we present revenue by customer vertical. We now report three customer verticals: service providers, enterprises and web giants compared to only service providers and enterprises in prior years. We believe this new presentation will provide more transparency into our exposure to web giant revenue which was previously primarily accounted for in enterprise revenue. The revenue by vertical percentages from prior years included in this report have been revised to conform with current year presentation. Our end-customers operate in a variety of industries, including telecommunications, technology, industrial, retail, financial, gaming, education and government. Since inception, our customer base has grown rapidly. As of  December 31, 2018 , we had sold products to approximately  6,000 end customers across 117 countries. We sell substantially all of our solutions through our high-touch sales organization as well as distribution channel partners, including distributors, value- added resellers and system integrators, and fulfill nearly all orders globally through such partners. We believe this sales approach allows us to obtain the benefits of channel distribution, such as expanding our market coverage, while still maintaining face-to-face relationships with our end-customers. We outsource the manufacturing of our hardware products to original design manufacturers. We perform quality assurance and testing at our San Jose, Taiwan and Japan distribution centers, as well as at our manufacturers’ locations. During 2018 ,  45%  of our total revenue was generated from the United States,  24%  from Japan and  31%  from other geographical regions. During 2017 ,  49%  of our total revenue was generated from the United States,  22%  from Japan and  29%  from other geographical regions. During 2016 , 51% of our total revenue was generated from the United States,  23% from Japan and 26% from other geographical regions. Our enterprise customers accounted for 39% , 39% and 41% of our total revenue during 2018 , 2017 and 2016 , respectively. Our service provider customers accounted for 43% , 47% and 48% of our 43 total revenue during 2018 , 2017 and 2016 , respectively. Our web giant customers accounted for 18% , 14% and 11% of our total revenue during 2018 , 2017 and 2016 , respectively. As a result of the nature of our target market and the current stage of our development, a substantial portion of our revenue comes from a limited number of large customers, including service providers and web giants, in any period. Purchases from our ten largest end-customers accounted for 37% , 35% and 36% of our total revenue for 2018 , 2017 and 2016 , respectively. Sales to these large end-customers have typically been characterized by large but irregular purchases with long sales cycles. The timing of these purchases and the delivery of the purchased products are difficult to predict. Consequently, any acceleration or delay in anticipated product purchases by or deliveries to our largest customers could materially impact our revenue and operating results in any quarterly period. This may cause our quarterly revenue and operating results to fluctuate from quarter to quarter and make them difficult to predict. As of December 31, 2018 , we had $40.6 million of cash and cash equivalents and $87.8 million of marketable securities. Cash used in operating activities was $2.7 million in 2018 compared to $14.3 million of cash provided by operating activities last year. We intend to continue to invest for long-term growth. We have invested and expect to continue to invest in our product development efforts to deliver new products and additional features in our current products to address customer needs. In addition, we may expand our global sales and marketing organizations, expand our distribution channel partner programs and increase awareness of our solutions on a global basis. Our investments in growth in these areas may affect our short-term profitability. 44 Results of Operations A summary of our consolidated statements of operations for the year ended December 31, 2018 , 2017 and 2016 are as follows (dollars in thousands): Years Ended December 31, 2018 2017 Increase (Decrease) Amount Percent of Total Revenue Amount Percent of Total Revenue Amount Percent $ 144,682   62.3 %   $ 149,903   63.7 %   $ Revenue: Products Services Total revenue Cost of revenue: Products Services Total cost of revenue Gross profit Operating expenses: Sales and marketing Research and development General and administrative Total operating expenses Loss from operations Non-operating income (expense): Interest expense Interest and other income (expense), net Total non-operating income (expense), net Loss before income taxes Provision for income taxes Net loss 87,541   232,223   34,066   17,830   51,896   180,327   103,214   65,157   39,635   208,006   (27,679)   (129)   1,273   1,144   (26,535)   1,082   37.7 100.0 14.7 7.6 22.3 77.7 44.4 28.1 17.1 89.6 (11.9) (0.1) 0.6 0.5 (11.4) 0.5 85,526   235,429   36,269   17,049   53,318   182,111   101,360   62,991   28,132   192,483   (10,372)   (162)   989   827   (9,545)   1,206   36.3 100.0 15.4 7.2 22.6 77.4 43.1 26.8 11.9 81.8 (4.4) (5,221)   2,015   (3,206)   (2,203)   781   (1,422)   (1,784)   1,854   2,166   11,503   15,523   (3.5)% 2.4 % (1.4)% (6.1)% 4.6 % (2.7)% (1.0)% 1.8 % 3.4 % 40.9 % 8.1 % (17,307)   (166.9)% —   0.3 0.3 (4.1) 0.5 33   284   317   (16,990)   (124)   20.4 % 28.7 % 38.3 % (178.0)% (10.3)% (156.9)% $ (27,617)   (11.9)%   $ (10,751)   (4.6)%   $ (16,866)   45                                                                                                                                                                                                           Years Ended December 31, 2017 2016 Increase (Decrease) Amount Percent of Total Revenue Amount Percent of Total Revenue Amount Percent $ 149,903   63.7 %   $ 152,308   67.0 %   $ 85,526   235,429   36,269   17,049   53,318   182,111   101,360   62,991   28,132   —   192,483   (10,372)   (162)   989   827   (9,545)   1,206   36.3 100.0 15.4 7.2 22.6 77.4 43.1 26.8 11.9 —   81.8 (4.4) —   0.3 0.3 (4.1) 0.5 74,989   227,297   37,520   16,893   54,413   172,884   104,360   60,700   26,305   2,089   193,454   (20,570)   (424)   (640)   (1,064)   (21,634)   757   33.0 100.0 16.5 7.4 23.9 76.1 45.9 26.7 11.6 0.9 85.1 (9.0) (0.2) (0.3) (0.5) (9.5) 0.4 (2,405)   10,537   8,132   (1,251)   156   (1,095)   9,227   (3,000)   2,291   1,827   (2,089)   (971)   10,198   262   1,629   1,891   12,089   449   $ (10,751)   (4.6)%   $ (22,391)   (9.9)%   $ 11,640   (1.6)% 14.1 % 3.6 % (3.3)% 0.9 % (2.0)% 5.3 % (2.9)% 3.8 % 6.9 % (100.0)% (0.5)% 49.6 % 61.8 % 254.5 % 177.7 % 55.9 % 59.3 % 52.0 % Revenue: Products Services Total revenue Cost of revenue: Products Services Total cost of revenue Gross profit Operating expenses: Sales and marketing Research and development General and administrative Litigation settlement expense Total operating expenses Loss from operations Non-operating income (expense): Interest expense Interest and other income (expense), net Total non-operating income (expense), net Loss before income taxes Provision for income taxes Net loss Revenue Our products revenue primarily consists of revenue from sales of our hardware appliances upon which our software is installed. Such software includes our ACOS software platform plus one or more of our ADC, CGN, TPS, SSLi or CFW solutions. Purchase of a hardware appliance includes a perpetual license to the included software. We recognize products revenue upon transfer of control, generally at the time of shipment, provided that all other revenue recognition criteria have been met. As a percentage of revenue, our products revenue may vary from quarter to quarter based on, among other things, the timing of orders and delivery of products, cyclicality and seasonality, changes in currency exchange rates and the impact of significant transactions with unique terms and conditions. We generate services revenue from sales of post contract support (“PCS”), which is bundled with sales of products and professional services. We offer tiered PCS services under renewable, fee-based PCS contracts, primarily including technical support, hardware repair and replacement parts, and software upgrades on a when-and-if-available basis. We recognize services revenue ratably over the term of the PCS contract, which is typically one year, but can be up to five years. Our adoption of ASC 606, the new revenue recognition guidance, in January 2018 resulted in a $2.6 million increase in products revenue in 2018. See Note  2  of the Notes to Consolidated Financial Statements in Part II, Item 8 of this report for additional information. 46                                                                                                                                                                                                             A summary of our total revenue is as follows (dollars in thousands): Years Ended December 31, 2018 2017 Increase (Decrease) Amount Percent of Total Revenue Amount Percent of Total Revenue Amount Percent $ $ $ 144,682   87,541   232,223   62%   $ 149,903   64%   $ 38 85,526   36 100%   $ 235,429   100%   $ (5,221)   2,015   (3,206)   103,791   45%   $ 115,536   49%   $ (11,745)   55,205   36,897   27,615   8,715   24 16 12 3 51,488   33,189   27,859   7,357   22 14 12 3 3,717   3,708   (244)   1,358   $ 232,223   100%   $ 235,429   100%   $ (3,206)   (3)% 2 % (1)% (10)% 7 % 11 % (1)% 18 % (1)% Years Ended December 31, 2017 2016 Increase (Decrease) Amount Percent of Total Revenue Amount Percent of Total Revenue Amount Percent $ $ $ 149,903   85,526   235,429   64%   $ 152,308   36 74,989   100%   $ 227,297   67%   $ 33 100%   $ 115,536   49%   $ 115,706   51%   $ 51,488   33,189   27,859   7,357   22 14 12 3 52,951   29,829   23,669   5,142   23 13 10 3 $ 235,429   100%   $ 227,297   100%   $ (2,405)   10,537   8,132   (170)   (1,463)   3,360   4,190   2,215   8,132   (2)% 14 % 4 % — % (3)% 11 % 18 % 43 % 4 % Revenue: Products Services Total revenue Revenue by geographic region: United States Japan Asia Pacific, excluding Japan EMEA Latin America Total revenue Revenue: Products Services Total revenue Revenue by geographic region: United States Japan Asia Pacific, excluding Japan EMEA Latin America Total revenue 2018 Revenue Compared to 2017 Revenue Total revenue decreased by  $3.2 million , or  1% , in 2018 compared to 2017 . This decrease was due to a $5.2 million  decrease in products revenue, partially offset by a $2.0 million  increase in services revenue. The decrease in products revenue was primarily driven by lower demand from our service provider customers in the United States. Revenue from web giant customers increased 26% and revenue from service provider customers decreased 10% in 2018 compared to 2017. Revenue from enterprise customers remained relatively constant in 2018 compared to 2017 . Products revenue decreased $5.2 million , or 3% , in 2018 compared to 2017 primarily driven by lower demand from our service provider customers in the United States, as well as decreases from EMEA, offset in part by a $2.6 million increase from the adoption of ASC 606 in 2018 and by the increase in products revenue primarily from Japan and Asia Pacific. See Note  2  of the Notes to Consolidated Financial Statements in Part II, Item 8 of this report for additional information related to our adoption of ASC 606. 47                                                                                                                                                                                                                           Services revenue increased $2.0 million , or 2% , in 2018 compared to 2017 . The increases were primarily attributable to the increase in PCS sales in connection with our increased installed customer base. During 2018 ,  $103.8 million , or  45% of total revenue, was generated from the United States, which represents a  10% decrease compared to 2017 . The decrease was primarily due to lower products revenue driven by lower demand from our service providers in the United States. During 2018 ,  $55.2 million , or  24% of total revenue, was generated from Japan, which represents a 7% increase compared to 2017 . The increase was mainly due to higher products revenue driven primarily by higher demand from our service providers in Japan. During 2018 ,  $36.9 million , or  16% of total revenue, was generated from the Asia Pacific region excluding Japan, which represents a  11% increase compared to 2017 . The increase was driven primarily by higher products revenue as well as higher services revenue from PCS sales in connection with our increased installed customer base. During 2018 ,  $27.6 million , or  12% of total revenue, was generated from EMEA, which remained relatively consistent from 2017 . 2017 Revenue Compared to 2016 Revenue Total revenue increased $8.1 million , or 4% , in 2017 compared to 2016 , due to a $10.5 million increase in services revenue, partially offset by a $2.4 million decrease in products revenue. Revenue from web giant and service provider customers increased 35% and 2% , respectively, in 2017 compared to 2016 . Revenue from enterprise customers decreased 3% in 2017 compared to 2016 . Products revenue decreased $2.4 million , or 2% , in 2017 compared to 2016 , which is primarily attributable to decreases from the United States and Japan, partially offset by increases from EMEA and Asia Pacific excluding Japan. Products revenue from service provider and enterprise customers increased  11%  and decreased  11% , respectively, in  2017  compared to  2016 . Services revenue increased $10.5 million , or 14% , in 2017 compared to 2016 , which is primarily attributable to the increase in PCS sales in connection with our increased installed customer base. During 2017 , services revenue recognized from our installed customer base with contracts existing at the beginning of the year grew by 19% compared to the same measure in 2016 . Services revenue from service provider and enterprise customers increased 11% and 16% , respectively, in 2017 compared to 2016. During 2017 , $115.5 million , or 49% , of total revenue was generated from the United States, which remained relatively constant compared to 2016 . The decrease in products revenue was partially offset by higher services revenue attributable to the increase PCS sales in connection with our increased installed customer base. During 2017 ,  $51.5 million , or  22% , of total revenue was generated from Japan, which represents a  3%  decrease in revenue compared to 2016 . The decrease in products revenue was partially offset by higher services revenue attributable to the increase PCS sales in connection with our increased installed customer base. During 2017 ,  $33.2 million , or  14% , of total revenue was generated from the Asia Pacific regions excluding Japan, which represents a  11% increase in revenue compared to 2016 . The increase was due to higher products revenue and higher services revenue from PCS sales in connection with our increased installed customer base. During 2017 ,  $27.9 million , or  12% , of total revenue was generated from EMEA, which represents a  18%  increase in revenue compared to 2016 . The increase was due to higher products revenue and higher services revenue from PCS sales in connection with our increased installed customer base. 48   Cost of Revenue, Gross Profit and Gross Margin Cost of revenue Cost of products revenue is primarily comprised of cost of third-party manufacturing services and cost of inventory for the hardware component of our products. Cost of products revenue also includes warehouse personnel costs, shipping costs, inventory write-downs, certain allocated facilities and information technology infrastructure costs, and expenses associated with logistics and quality control. Cost of services revenue is primarily comprised of personnel costs for our technical support, training and professional service teams. Cost of services revenue also includes the costs of inventory used to provide hardware replacements to end- customers under PCS contracts and certain allocated facilities and information technology infrastructure costs. A summary of our cost of revenue is as follows (dollars in thousands): Cost of revenue: Products Services Total cost of revenue Cost of revenue: Products Services Total cost of revenue Gross Margin Years Ended December 31, Increase (Decrease) 2018 2017 Amount Percent 34,066   $ 17,830   51,896   $ 36,269   $ 17,049   53,318   $ (2,203)   781   (1,422)   Years Ended December 31, Increase (Decrease) 2017 2016 Amount Percent 36,269   $ 17,049   53,318   $ 37,520   $ 16,893   54,413   $ (1,251)   156   (1,095)   (6)% 5 % (3)% (3)% 1 % (2)% $ $ $ $ Gross margin may vary and be unpredictable from period to period due to a variety of factors. These may include the mix of revenue from each of our regions, the mix of our products sold within a period, discounts provided to customers, inventory write-downs and foreign currency exchange rates.  Our sales are generally denominated in U.S. dollars, however, in Japan they are denominated in Japanese yen. Any of the factors noted above can generate either a favorable or unfavorable impact on gross margin. A summary of our gross profit and gross margin is as follows (dollars in thousands): Gross profit: Products Services Total gross profit Years Ended December 31, 2018 2017 Increase (Decrease) Amount Gross Margin Amount Gross Margin Amount Gross Margin $ $ 110,616   69,711   180,327   76.5%   $ 113,634   79.6%   68,477   77.7%   $ 182,111   75.8%   $ 80.1%   77.4%   $ (3,018)   1,234   (1,784)   0.7 % (0.5)% 0.3 % 49                                                                                                                       Gross profit: Products Services Total gross profit Years Ended December 31, 2017 2016 Increase (Decrease) Amount Gross Margin Amount Gross Margin Amount Gross Margin $ $ 113,634   68,477   182,111   75.8%   $ 114,788   80.1%   58,096   77.4%   $ 172,884   75.4%   $ 77.5%   76.1%   $ (1,154)   10,381   9,227   0.4% 2.6% 1.3% 2018 Gross Margin Compared to 2017 Gross Margin Products gross margin increased 0.7% in 2018 compared to 2017 primarily driven by a favorable impact from our product mix. Services gross margin decreased 0.5% in 2018  compared to 2017 primarily due to higher costs of inventory used to provide hardware replacements to end customers under PCS contracts and higher personnel related support costs. 2017 Gross Margin Compared to 2016 Gross Margin Products gross margin increased by  0.4%  in  2017  compared to  2016  primarily due to the favorable impact as a result of lower inventory reserve for excess and obsolete products, partially offset by unfavorable geographic revenue mix. We had less sales from geographic regions and products with higher gross margins in  2017  compared to  2016 . Services gross margin increased by 2.6% in 2017 compared to 2016 primarily due to higher services revenue due to increased installed customer base while the personnel costs related to support, professional services and maintenance remained relatively constant. Operating Expenses Our operating expenses consist of sales and marketing, research and development, general and administrative, and litigation settlement expenses. The largest component of our operating expenses is personnel costs which consist of wages, benefits, bonuses, and, with respect to sales and marketing expenses, sales commissions. Personnel costs also include stock-based compensation. A summary of our operating expenses is as follows (dollars in thousands): Operating expenses: Sales and marketing Research and development General and administrative Total operating expenses Years Ended December 31, Increase (Decrease) 2018 2017 Amount Percent $ $ 103,214   $ 101,360   $ 65,157   39,635   62,991   28,132   208,006   $ 192,483   $ 1,854   2,166   11,503   15,523   2% 3% 41% 8% 50                                                                                               Operating expenses: Sales and marketing Research and development General and administrative Litigation settlement expense Total operating expenses Sales and Marketing Years Ended December 31, Increase (Decrease) 2017 2016 Amount Percent $ $ 101,360   $ 104,360   $ 62,991   28,132   —   60,700   26,305   2,089   192,483   $ 193,454   $ (3,000)   2,291   1,827   (2,089)   (971)   (3)% 4 % 7 % (100)% (1)% Sales and marketing expenses are our largest functional category of operating expenses and primarily consist of personnel costs. Sales and marketing expenses also include the cost of marketing programs, trade shows, consulting services, promotional materials, demonstration equipment, depreciation and certain allocated facilities and information technology infrastructure costs. Prior to the adoption of ASC 606, we expensed sales commissions associated with the acquisition of customer contracts as incurred in the period the contract was acquired. Upon the adoption of ASC 606 in January 2018, $8.4 million of our sales commission expenses from prior periods has been deferred and will be recognized over an expected benefit period as required by ASC 340-40, Other Assets and Deferred Costs - Contracts with Customers. See Note  2  of the Notes to Consolidated Financial Statements in Part II, Item 8 of this report for additional information. The increase in sales and marketing expenses in 2018 compared to 2017 was primarily due to a $6.0 million increase in sales commissions driven by higher bookings and higher average commission rate in 2018, offset by a $1.3 million decrease in sales commissions from the adoption of ASC 340-40 in 2018. The increase in sales and marketing expenses was also offset by a $2.4 million decrease in employee compensation and benefits driven primarily by decreased headcount resulted from improved sales productivity and a $0.8 million decrease in contractor costs. The decrease in sales and marketing expenses in 2017 compared to 2016 was primarily attributable to a $2.2 million decrease in personnel costs as a result of lower sales commissions and a $0.9 million decrease in travel and entertainment. We expect sales and marketing expenses to decrease in 2019 as a result of the transformation of our sales organization that started in early 2018. Research and Development Research and development efforts are focused on new product development and on developing additional functionality for our existing products. These expenses primarily consist of personnel costs, and, to a lesser extent, prototype materials, depreciation and certain allocated facilities and information technology infrastructure costs. We expense research and development costs as incurred. The increase in research and development expenses in 2018 compared to 2017 was primarily driven by a $2.3 million increase in employee bonuses and a $0.9 million increase in consultant fees, offset by a $1.1 million decrease in salaries and wages due to a change of geographic mix in headcount. The increase in research and development expenses in 2017 compared to 2016 was primarily attributable to a $1.0 million increase in personnel costs, a $0.5 million increase in contractor and consultant fees, a $0.4 million increase in expensed equipment and software subscription and a $0.4 million increase in depreciation expense. We expect research and development expenses for 2019 to be relatively consistent with 2018. General and Administrative General and administrative expenses primarily consist of personnel costs, professional services and office expenses. General and administrative personnel costs include executive, finance, human resources, information technology, facility and 51                                         legal (excluding litigation settlement) related expenses. Professional services primarily consist of fees for outside accounting, tax, legal, recruiting and other administrative services. The increase in general and administrative expenses in 2018 compared to 2017 was primarily driven by the $8.6 million internal investigation related fees we incurred in 2018 as we previously disclosed, a $1.6 million increase in contractor and consultant fees primarily for supporting the accounting function and a $0.8 million increase in employee compensation and benefits. The increase in general and administrative expenses in 2017 compared to 2016 was primarily attributable to a $0.7 million increase in business and office expenses, a $0.5 million increase in personnel costs and a $0.5 million increase in recruiting fees. We expect general and administrative expenses for 2019 to decrease in 2018 due to lower accounting and legal costs. Litigation Settlement Expense Litigation settlement expense is comprised of legal expenses incurred related to intellectual property-related litigation settlement and certain charges for litigation reserves. Litigation settlement expenses consist of professional fees incurred in defending ourselves against such litigation matters and are expensed as incurred when professional services are provided. The litigation reserve, if any, consists of accruals we make related to estimated losses in such pending legal proceedings. Litigation reserves, if any, are adjusted as we change our estimates or make payments in damages or settlements. Litigation settlement expense of  $2.1 million in 2016 was due to the class action and the derivative action lawsuits which were settled in the second quarter of 2016. We had no such intellectual property-related litigation settlement expense incurred in 2018 and 2017. Interest Expense Interest expense consists primarily of interest expense and amortization of debt issuance costs. At December 31, 2018 , we had no outstanding balances on our credit facility. We expect to continue to incur commitment fees associated with the undrawn balance of our credit facility. If we choose to draw down on the credit facility, at such time, we would reduce the commitment fees accrued and increase the interest on outstanding balances. Interest expense was immaterial in 2018 , 2017 and 2016 . Interest and Other Income (Expense), Net Interest income consists primarily of interest income earned on our cash and cash equivalents and marketable securities. Other income (expense) consists primarily of foreign currency exchange gains and losses. Interest and other income (expense), net, had a favorable change of $0.3 million , or 29% , in 2018 compared to 2017 primarily driven by a $0.7 million increase in interest income, offset by a $0.3 million increase in foreign exchange loss. Interest and other income (expense), net, had a favorable change of $1.6 million , or 255% , in 2017 compared to 2016 primarily due to a $1.2 million increase in foreign exchange gain and a $0.4 million increase in interest income. Provision for Income Taxes We recorded an income tax provision of $1.1 million , $1.2 million and $0.8 million for the year ended December 31, 2018 , 2017 and 2016 , respectively, which primarily consisted of foreign taxes. We currently maintain a valuation allowance on federal and state deferred tax assets, and we will continue to maintain a valuation allowance against all of our U.S. and certain foreign deferred tax assets until there is sufficient evidence to support the reversal of all or some portion of this allowance. 52 On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act makes broad and complex changes to the U.S. tax code including, but not limited to: (1) reducing the U.S. federal corporate tax rate from 35 percent to 21 percent; (2) requiring companies to pay a one-time transition tax on certain unrepatriated earnings of foreign subsidiaries; (3) generally eliminating U.S. federal income taxes on dividends from foreign subsidiaries; (4) requiring a current inclusion in U.S. federal taxable income of certain earnings of controlled foreign corporations; (5) eliminating the corporate alternative minimum tax (“AMT”) and changing how existing AMT credits can be realized; (6) creating the base erosion anti-abuse tax, a new minimum tax; (7) creating a new limitation on deductible interest expense; and (8) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017. As a result of the reduction in the U.S. corporate income tax rate, we revalued our U.S. net deferred tax asset at December 31, 2017. The revaluation is based on the rates at which the U.S. net deferred tax assets are expected to reverse in the future. There was no impact to the balance sheet and income statement due to the full valuation allowance placed on the deferred tax assets for the U.S. See Note 9 to the consolidated financial statements in Part II, Item 8 for further details. Liquidity and Capital Resources As of December 31, 2018 , we had cash and cash equivalents of $40.6 million , including $8.6 million held outside the United States in our foreign subsidiaries, and $87.8 million of marketable securities. We currently do not have any plans to repatriate our earnings from our foreign operations. As of December 31, 2018 , we had working capital of $117.6 million , accumulated deficit of $272.2 million and total stockholders’ equity of $103.9 million . We plan to continue to invest for long-term growth, and our investment may increase. We believe that our existing cash and cash equivalents, marketable securities and other available financial resources will be sufficient to meet our anticipated cash needs for at least the next 12 months. Our future capital requirements will depend on many factors, including our growth rate, the expansion of sales and marketing activities, the timing and extent of spending to support development efforts, the introduction of new and enhanced product and service offerings and the continuing market acceptance of our products. In the event that additional financing is required from outside sources, we may not be able to raise such financing on terms acceptable to us or at all. If we are unable to raise additional capital when desired, our business, operating results and financial condition could be adversely affected. On October 23, 2017, our board of directors authorized a share repurchase program for up to $20.0 million of our common stock over 12 months.  No shares were repurchased under this program through its expiration in October 2018. In addition, as described in Note 6 in the Notes to the Consolidated Financial Statements in this report, we are currently, or from time to time, involved in ongoing litigation. Any adverse settlements or judgments in any litigation could have a material adverse impact on our results of operations, cash balances and cash flows in the period in which such events occur. Credit Agreements In November 2016, we entered into the 2016 Credit Facility with Silicon Valley Bank (“SVB”) as the lender. The 2016 Credit Facility provides a three - year, $25.0 million revolving credit facility, which includes a maximum of $25.0 million letter of credit subfacility. When the balance of our cash, cash equivalents and marketable securities minus outstanding revolving loans and letters of credit equals or exceeds $50.0 million, loans may be advanced under the 2016 Credit Facility up to the full $25.0 million. When the balance of our cash, cash equivalents and marketable securities minus outstanding revolving loans and letters of credit falls below $50.0 million, loans may be advanced under the 2016 Credit Facility based on a borrowing base equal to a specified percentage of the value of our eligible accounts receivable. The loans bear interest, at our option, at (i) the prime rate reported in The Wall Street Journal, minus 0.50% or (ii) a LIBOR rate determined in accordance with the 2016 Credit Facility, plus 2.50%. In September 2018, we entered into an amendment with SVB to reduce the unused revolving line facility fee on the 2016 Credit Facility from 0.4% to 0.3%. Our obligations under the 2016 Credit Facility are secured by substantially all of our assets, excluding our intellectual property. The 2016 Credit Facility contains customary affirmative and negative covenants, in each case subject to customary 53 exceptions, and customary events of default. In addition, the 2016 Credit Facility requires us to maintain compliance with an adjusted quick ratio of not less than 1.50:1.00, as determined in accordance with the 2016 Credit Facility. The 2016 Credit Facility also restricts our ability to pay cash dividends or make other distributions on our capital stock. As of  December 31, 2018 , we had no outstanding balance under the 2016 Credit Facility and were in compliance with all facility covenants. Statements of Cash Flows The following table summarizes our cash flow related activities (in thousands): Cash (used in) provided by: Operating activities Investing activities Financing activities Net (decrease)  increase  in cash and cash equivalents Cash Flows from Operating Activities Years Ended December 31, 2018 2017 2016 $ $ (2,694)   $ 14,314   $ (6,876)   3,624   (5,142)   8,420   (5,946)   $ 17,592   $ 18,778 (96,355) 8,435 (69,142) Our cash provided by operating activities is driven primarily by sales of our products and management of working capital investments. Our primary uses of cash from operating activities have been for personnel-related expenditures, manufacturing costs, marketing and promotional expenses and costs related to our facilities. Our cash flows from operating activities will continue to be affected principally by the extent to which we increase spending on our business and our working capital requirements. During the year ended December 31, 2018 , cash used in operating activities was $2.7 million , consisting of net loss of $27.6 million which includes payments for our internal investigation costs of $8.6 million , non-cash charges of $25.0 million and an unfavorable net change in operating assets and liabilities of $0.1 million . Our non-cash charges consisted primarily of stock-based compensation expense of $17.0 million and depreciation and amortization expenses of $7.9 million . The net change in our operating assets and liabilities primarily reflects an inflow from the changes in deferred revenue of $7.3 million and accrued and other liabilities of $3.1 million , offset primarily by an outflow from the changes in accounts receivable of $6.1 million , prepaid expenses and other assets of $2.4 million and inventory of $1.5 million . The favorable change in deferred revenue was primarily driven by the increase in the sale of subscription and support. The favorable change in accrued and other liabilities was primarily due to higher accrued bonuses and commissions, increased value added tax accrual due to timing of payments, and an increase in legal fees accrual. The unfavorable change in accounts receivable was attributed to timing of billing and cash collections. The unfavorable change in prepaid and other assets was mainly driven by the increase in deferred sales commissions due to higher deferred revenue and higher average commission rate. The unfavorable change in inventory was due to the timing of shipments. During the year ended December 31, 2017 , cash provided by operating activities was $14.3 million , consisting of a net loss of $10.8 million , a cash decrease resulting from the net change in operating assets and liabilities of $1.4 million and non-cash charges of $26.4 million . Our non-cash charges consisted primarily of stock-based compensation of $17.2 million , depreciation and amortization of $8.5 million and provision for doubtful accounts and sales returns allowance of $1.1 million . The net change in our operating assets and liabilities primarily reflects an inflow from the changes in accounts receivable of $12.4 million and deferred revenue of $3.0 million , and an outflow from the change in accrued liabilities of $8.9 million , inventory of $4.7 million , prepaid expenses and other assets of  $2.4 million and accounts payable of  $0.9 million . The decrease in accounts receivable was primarily due to the timing of billing and cash collections. The increase in deferred revenue was primarily due to higher contract renewals. The decrease in accrued liabilities was primarily due to lower accrued bonuses and commissions. The increase in inventory was primarily due to lower product shipments. The increase in prepaid expenses and other assets was primarily due to prepaid royalties, software subscription renewals and prepaid expenses and deposit related to a sales event. The decrease in accounts payable was primarily due to the timing of vendor invoice payments. 54                               During the year ended December 31, 2016 , cash provided by operating activities was  $18.8 million , consisting of a net loss of  $22.4 million , a cash increase resulting from the net change in operating assets and liabilities of $13.5 million  and non-cash charges of $27.6 million . Our non-cash charges consisted primarily of stock-based compensation of  $16.9 million , depreciation and amortization of  $8.3 million  and provision for doubtful accounts and sales returns allowance of  $1.6 million . The net change in our operating assets and liabilities primarily reflect an inflow from the changes in deferred revenue of  $19.6 million , accrued liabilities of  $3.1 million  and inventory of  $0.5 million , and an outflow from the change in accounts receivable of $8.7 million . Cash Flows from Investing Activities During the year ended December 31, 2018 , cash used in investing activities was $6.9 million , consisting of purchases of property and equipment of $2.8 million , marketable securities of $86.8 million and investment of $1.0 million , partially offset by proceeds from sales and maturities of marketable securities of $83.7 million . During the  year ended December 31, 2017 , cash used in investing activities was  $5.1 million , consisting of purchases of property and equipment of  $5.7 million and marketable securities of $87.4 million , partially offset by proceeds from sales and maturities of marketable securities of $88.0 million . During the year ended December 31, 2016 , cash used in investing activities was  $96.4 million , primarily consisting of purchases of property and equipment of $4.9 million, payment for the acquisition of substantially all of the assets of Appcito Inc. of $4.4 million, purchase of an intangible asset of $1.5 million, purchases of marketable securities of $126.2 million , offset by proceeds from sales and maturities of marketable securities of $40.6 million . Cash Flows from Financing Activities During the year ended December 31, 2018 , cash provided by financing activities was $3.6 million consisting primarily of proceeds from common stock issuances under our equity incentive plans.  During the year ended December 31, 2017 , cash provided by financing activities was $8.4 million , primarily consisting of proceeds from common stock issuances under our equity incentive plans of  $12.2 million , partially offset by repurchase and retirement of common stock of $3.1 million  and payment of contingent consideration of  $0.7 million . During the year ended December 31, 2016 , cash provided by financing activities was  $8.4 million , primarily consisting of proceeds from common stock of issuances under our equity incentive plans of $10.3 million , partially offset by the stock repurchase and retirement of common stock of $1.8 million . Contractual Obligations Our contractual obligations consist of operating leases, purchase commitments, and other contractual obligation.  The following table summarizes our contractual obligations as of December 31, 2018 (in thousands): Operating leases and other contractual obligation Purchase commitments (1) Total Total Less Than 1 Year 1 to 3 Years 3 to 5 Years More than 5 years $ $ 7,335   $ 3,907   $ 3,428   $ 19,296   19,296   —   26,631   $ 23,203   $ 3,428   $ —   $ —   —   $ — — — (1) Amount represents our purchase commitments for inventory. See Note 6 to the consolidated financial statements for additional information. The contractual obligations table above excludes $4.2 million of tax liabilities related to uncertain tax positions because we are unable to make a reasonably reliable estimate of the timing of settlement, if any, of these future payments. 55             Off-Balance Sheet Arrangements As of December 31, 2018 , we did not have any off-balance sheet arrangements or relationships with unconsolidated entities or financial partnerships, such as entities often referred to as structured finance or special purpose entities that are typically established for the purpose of facilitating off-balance sheet arrangements or other contractually narrow or limited purposes. Critical Accounting Policies and Estimates Our consolidated financial statements are prepared in accordance with generally accepted accounting principles in the United States. The preparation of these consolidated financial statements requires us to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue, expenses and related disclosures. We evaluate our estimates and assumptions on an ongoing basis. Our estimates are based on historical experience and various other assumptions that we believe to be reasonable under the circumstances. Our actual results could differ from these estimates. We believe the following critical accounting policies require us to make significant judgments and estimates in the preparation of our consolidated financial statements. Inventory Inventory consists primarily of finished goods and related component parts and is stated at the lower of standard cost (which approximates actual cost on a first-in, first-out basis) or estimated net realizable value. We evaluate inventory for excess and obsolete products, based on management’s assessment of future demand and market conditions. Inventory write-downs, once established, are not reversed as they establish a new cost basis for the inventory. Inventory write downs are included as a component of cost of products revenue in the accompanying consolidated statements of operations. Revenue Recognition We  derive  revenue  from  two  sources:  (i)  products  revenue,  which  includes  hardware,  perpetual  software  license  and  subscription  revenue;  and  (ii) services  revenue,  which  includes  post  contract  support  (“PCS”),  professional  services,  and  training.  A  substantial  portion  of  our  revenue  is  from  sales  of  our products  and  services  through  distribution  channel  partners,  such  as  resellers  and  distributors.  Revenue  is  recognized,  net  of  applicable  taxes,  upon  transfer  of control of promised products or services to customers in an amount that reflects the consideration we expect to be entitled to receive in exchange for those products or services. We apply the following five-step revenue recognition model: • • • • • Identification of the contract, or contracts, with a customer Identification of the performance obligations in the contract Determination of the transaction price Allocation of the transaction price to the performance obligations in the contract Recognition of revenue when, or as, performance obligations are satisfied. PCS revenue includes arrangements for software support and technical support for our products. PCS is offered under renewable, fee-based contracts, which include technical support, hardware repair and replacement parts, bug fixes, patches, and unspecified upgrades on a when-and-if available basis. Revenue for PCS services is recognized on a straight-line basis over the service contract term, which is typically one year, but can be up to five years as there is no discernable pattern of transfer related to these promises. Billed but unearned PCS revenue is included in deferred revenue. Professional service revenue primarily   consists of the fees we earn related to installation and consulting services. We recognize revenue from professional services upon delivery or completion of performance. Professional service arrangements are typically short term in nature and are largely completed within 30 to 90 days from the start of service. Revenue is recognized for training when the training course is delivered. 56 Contracts with Multiple Performance Obligations Most of our contracts with customers, other than renewals of PCS, contain multiple performance obligations with a combination of products and PCS. Products and PCS generally qualify as distinct performance obligations. Our hardware includes embedded ACOS software, which together deliver the essential functionality of our products. For contracts which contain multiple performance obligations, we allocate revenue to each distinct performance obligation based on the standalone selling price (“SSP”). Judgment is required to determine the SSP for each distinct performance obligation. We use a range of amounts to estimate SSP for products and PCS sold together in a contract to determine whether there is a discount to be allocated based on the relative SSP of the various products and PCS. If we do not have an observable SSP, such as when we do not sell a product or service separately, then SSP is estimated using judgment and considering all reasonably available information such as market conditions and information about the size and/or purchase volume of the customer. We generally use a range of amounts to estimate SSP for individual products and services based on multiple factors including, but not limited to the sales channel (reseller, distributor or end customer), the geographies in which our products and services are sold, and the size of the end customer. We account for multiple contracts with a single partner as one arrangement if the contractual terms and/or substance of those agreements indicate that they may be so closely related that they are, in effect, parts of a single contract. We may occasionally accept returns to address customer satisfaction issues even though there is generally no contractual provision for such returns. We estimate  returns  for  sales  to  customers  based  on  historical  returns  rates  applied  against  current-period  shipments.  Specific  customer  returns  and  allowances  are considered when determining our sales return reserve estimate. Our  policy  applies  to  the  accounting  for  individual  contracts.  However,  we  have  elected  a  practical  expedient  to  apply  the  guidance  to  a  portfolio  of contracts  or  performance  obligations  with  similar  characteristics  so  long  as  such  application  would  not  differ  materially  from  applying  the  guidance  to  the individual contracts (or performance obligations) within that portfolio. Consequently,  we  have  chosen  to  apply  the  portfolio  approach  when  possible,  which  we  do  not  believe  will  happen  frequently.  Additionally,  we  will evaluate  a  portfolio  of  data,  when  possible,  in  various  situations,  including  accounting  for  commissions,  rights  of  return  and  transactions  with  variable consideration. Recent Accounting Pronouncements Refer to Note 1  in Item 8 of this Form 10-K for information related to recent accounting pronouncements. Item 7A. Quantitative and Qualitative Disclosures about Market Risk Foreign Currency Risk Our consolidated results of operations, financial position and cash flows are subject to fluctuations due to changes in foreign currency exchange rates. Historically, the majority of our revenue contracts are denominated in U.S. dollars, with the most significant exception being Japan where we invoice primarily in Japanese yen. Our costs and expenses are generally denominated in the currencies where our operations are located, which is primarily in North America, EMEA and, to a lesser extent, Japan and the Asia Pacific region. In 2016, we initiated a hedging program with respect to foreign currency risk. Revenue resulting from selling in local currencies and costs and expenses incurred in local currencies are exposed to foreign currency exchange rate fluctuations, which can affect our revenue and operating income. As exchange rates vary, operating income may differ from expectations. The functional currency of our foreign subsidiaries is the U.S. dollar. At the end of each reporting period, monetary assets and liabilities are remeasured to the functional currency using exchange rates in effect at the balance sheet date. Non-monetary assets and liabilities are remeasured at historical exchange rates. Gains and losses related to remeasurement are recorded in interest and other income (expense), net in the consolidated statements of operations. A significant fluctuation in the exchange rates between our subsidiaries’ local currencies, especially the Japanese yen, British Pound and Euro, and the U.S. dollar could have an adverse impact on our consolidated financial position and results of operations. 57 We recorded $0.7 million , $0.4 million and $1.6 million foreign exchange loss during the years ended December 31, 2018 , 2017 and 2016 , respectively. The effect of a hypothetical 10% change in our exchange rate would not have a significant impact on our consolidated results of operations. Interest Rate Sensitivity Our exposure to interest rates risk relates to our 2016 Credit Facility with variable interest rates, where an increase in interest rates may result in higher borrowing costs. Since we have no outstanding borrowings under our 2016 Credit Facility as of  December 31, 2018 , the effect of a hypothetical 10% change in interest rates would not have any impact on our interest expense.  Our exposure to market risk for changes in interest rates relates primarily to our marketable securities. Our marketable securities are comprised of certificates of deposit, corporate securities, U.S. Treasury and agency securities, commercial paper and asset-backed securities . We do not enter into investments for trading or speculative purposes. At  December 31, 2018 , our investment portfolio included marketable securities with an aggregate fair market value and amortized cost basis of  $87.8 million and $87.9 million , respectively.  The following table presents the hypothetical fair values of our marketable securities assuming immediate parallel shifts in the yield curve of 50 basis points (“BPS”), 100 BPS and 150 BPS as of  December 31, 2018  (in thousands): Marketable securities $ 88,534   $ 88,274   $ 88,014   $ 87,754   $ 87,494   $ 87,234   $ 86,974 (150 BPS) (100 BPS) (50 BPS) 12/31/2018 50 BPS 100 BPS 150 BPS   Fair Value as of 58                                       Item 8. Financial Statements and Supplementary Data Index to Consolidated Financial Statements Report of Independent Registered Public Accounting Firm Consolidated Balance Sheets as of December 31, 2018 and 2017 Consolidated Statements of Operations for the years ended December 31, 2018, 2017 and 2016 Consolidated Statements of Comprehensive Loss for the years ended December 31, 2018, 2017 and 2016 Consolidated Statements of Stockholders’ Equity for the years ended December 31, 2018, 2017 and 2016 Consolidated Statements of Cash Flows for the years ended December 31, 2018, 2017 and 2016 Notes to Consolidated Financial Statements 59 Page 60 61 62 63 64 65 66   Report of Independent Registered Public Accounting Firm To the Stockholders and the Board of Directors of A10 Networks, Inc. Opinion on the Financial Statements We have audited the accompanying consolidated balance sheets of A10 Networks, Inc. and subsidiaries (the “Company”) as of December 31, 2018 and 2017, the related consolidated statements of operations, comprehensive loss, stockholders’ equity, and cash flows, for each of the three years in the period ended December 31, 2018, and the related notes (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2018 and 2017, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2018, in conformity with accounting principles generally accepted in the United States of America. Change in Accounting Principle As discussed in Note 2 to the financial statements, the Company has changed its method of accounting for revenue from contracts with customers in 2018 due to the adoption of Accounting Standards Update No. 2014-09 Revenue from Contracts with Customers (Topic 606) using the modified retrospective approach. Basis for Opinion These financial statements are the responsibility of the Company's management. Our responsibility is to express an opinion on the Company's financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB. We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company’s internal control over financial reporting. Accordingly, we express no such opinion. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion. /S/ DELOITTE & TOUCHE LLP San Jose, California March 15, 2019 We have served as the Company’s auditor since 2011. 60 A10 NETWORKS, INC. CONSOLIDATED BALANCE SHEETS (in thousands, except par value) ASSETS Current assets: Cash and cash equivalents Marketable securities Accounts receivable, net of allowances of $319 and $983, respectively Inventory Prepaid expenses and other current assets Total current assets Property and equipment, net Goodwill Intangible assets Other non-current assets Total assets Current liabilities: Accounts payable Accrued liabilities Deferred revenue, current Total current liabilities Deferred revenue, non-current Other non-current liabilities Total liabilities LIABILITIES AND STOCKHOLDERS’ EQUITY Commitments and contingencies (Note 6) Stockholders' equity: Common stock, $0.00001 par value: 500,000 shares authorized; 74,301 and 71,692 shares issued and outstanding, respectively Additional paid-in-capital Accumulated other comprehensive loss Accumulated deficit Total stockholders' equity Total liabilities and stockholders' equity See accompanying notes to consolidated financial statements. 61 December 31, 2018 December 31, 2017 $ 40,621   $ 87,754   53,972   17,930   14,662   46,567 84,567 48,266 17,577 6,825 $ $ 214,939   203,802 7,262   1,307   3,748   8,620   9,913 1,307 5,190 4,646 235,876   $ 224,858 8,202   $ 25,291   63,874   97,367   34,092   534   9,033 21,835 61,858 92,726 32,779 967 131,993   126,472 1   376,272   (144)   (272,246)   103,883   $ 235,876   $ 1 355,533 (123) (257,025) 98,386 224,858                           Revenue: Products Services Total revenue Cost of revenue: Products Services Total cost of revenue Gross profit Operating expenses: Sales and marketing Research and development General and administrative Litigation settlement expense Total operating expenses Loss from operations Non-operating income (expense): Interest expense A10 NETWORKS, INC. CONSOLIDATED STATEMENTS OF OPERATIONS (in thousands, except per share amounts) Years Ended December 31, 2018 2017 2016 $ 144,682   $ 149,903   $ 87,541   232,223   34,066   17,830   51,896   180,327   103,214   65,157   39,635   —   208,006   (27,679)   (129)   1,273   1,144   (26,535)   1,082   (27,617)   (0.38)   $ $ 85,526   235,429   36,269   17,049   53,318   182,111   101,360   62,991   28,132   —   192,483   (10,372)   (162)   989   827   (9,545)   1,206   (10,751)   (0.15)   $ $ 152,308 74,989 227,297 37,520 16,893 54,413 172,884 104,360 60,700 26,305 2,089 193,454 (20,570) (424) (640) (1,064) (21,634) 757 (22,391) (0.34) Interest and other income (expense), net Total non-operating income (expense), net Loss before income taxes Provision for income taxes Net loss Net loss per share: Basic and diluted $ $ Weighted-average shares used in computing net loss per share: Basic and diluted 72,882   70,053   65,701   See accompanying notes to consolidated financial statements. 62                                                                                                                                             A10 NETWORKS, INC. CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (in thousands) Net loss Other comprehensive loss, net of tax: Unrealized loss on marketable securities Comprehensive loss Years Ended December 31, 2018 2017 2016 (27,617)   $ (10,751)   $ (22,391) (21)   (78)   (27,638)   $ (10,829)   $ (45) (22,436) $ $ See accompanying notes to consolidated financial statements. 63                                             Additional Paid- in Capital Accumulated Deficit Accumulated Other Comprehensive Loss Total Stockholders' Equity A10 NETWORKS, INC. CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (in thousands) Balance at December 31, 2015 Stock-based compensation expense Common stock issued under employee equity incentive plans Common stock issued under asset purchase agreement Vesting of early exercise stock options Repurchase and retirement of common stock Unrealized loss on marketable securities, net of tax Net loss Balance at December 31, 2016 Cumulative effect adjustment from adoption of ASU 2016-09 Stock-based compensation expense Common stock issued under employee equity incentive plans Vesting of early exercise stock options Repurchase and retirement of common stock Unrealized loss on marketable securities, net of tax Net loss Balance at December 31, 2017 Cumulative effect adjustment from adoption of ASU 2014-09  Stock-based compensation  expense Common stock issued under employee equity incentive plans Unrealized loss on marketable securities, net of tax Net loss Common Stock Shares Amount 64,172   $ —   3,664   227   37   (227)   —   —   67,873   —   —   4,256   14   (451)   —   —   71,692   —   —   2,609   —   —   1   $ 301,886   $ (223,682)   $ —   —   —   —   —   —   —   1   —   —   —   —   —   —   —   1   —   —   —   —   —   16,922   10,336   1,313   211   (1,799)   —   —   328,869   201   17,203   12,244   87   (3,071)   —   —   355,533   —   17,038   3,701   —   —   —   —   —   —   —   —   (22,391)   (246,073)   (201)   —   —   —   —   —   (10,751)   (257,025)   12,396   —   —   —   (27,617)   Balance at December 31, 2018 74,301   $ 1   $ 376,272   $ (272,246)   $ See accompanying notes to consolidated financial statements. 64 —   $ —   —   —   —   —   (45) —   (45) —   —   —   —   —   (78) —   (123) —   —   —   (21) —   (144)   $ 78,205 16,922 10,336 1,313 211 (1,799) (45) (22,391) 82,752 — 17,203 12,244 87 (3,071) (78) (10,751) 98,386 12,396 17,038 3,701 (21) (27,617) 103,883                                                                                                     A10 NETWORKS, INC. CONSOLIDATED STATEMENTS OF CASH FLOWS (in thousands) Cash flows from operating activities: Net loss Adjustments to reconcile net loss to net cash (used in)  provided by operating activities: Years Ended December 31, 2018 2017 2016 $ (27,617)   $ (10,751)   $ (22,391) Depreciation and amortization Stock-based compensation Provision for doubtful accounts and sales returns Other non-cash items Changes in operating assets and liabilities: Accounts receivable Inventory Prepaid expenses and other assets Accounts payable Accrued and other liabilities Deferred revenue Other Net cash  (used in)  provided by operating activities Cash flows from investing activities: Proceeds from sales of marketable securities Proceeds from maturities of marketable securities Purchases of marketable securities Purchase of investment Purchases of property and equipment Purchase of intangible asset Payment for acquisition Net cash used in  investing activities Cash flows from financing activities: Proceeds from issuance of common stock under employee equity incentive plans Repurchases and retirement of common stock Payment of contingent consideration Other Net cash provided by  financing activities Net (decrease)  increase  in cash and cash equivalents Cash and cash equivalents - beginning of period Cash and cash equivalents - end of period Supplemental Disclosures: Cash paid for income taxes, net of refunds Cash paid for interest Non-cash investing and financing activities: Inventory transfers to property and equipment Purchases of property and equipment included in accounts payable Common stock issued under asset purchase agreement Vesting of early exercised stock options 7,880   17,038   212   (68)   (6,119)   (1,529)   (2,434)   (603)   3,116   7,331   99   (2,694)   32,720   51,024   (86,823)   (1,000)   (2,797)   —   —   8,511   17,203   1,147   (422)   12,362   (4,669)   (2,399)   (942)   (8,868)   3,018   124   14,314   27,901   60,138   (87,447)   —   (5,734)   —   —   (6,876)   (5,142)   3,701   —   —   (77)   3,624   (5,946)   46,567   40,621   517   100   1,176   58   —   —   $ $ $ $ $ $ $ 12,244   (3,071)   (650)   (103)   8,420   17,592   28,975   46,567   1,108   111   2,946   286   —   87   $ $ $ $ $ $ $ $ $ $ $ $ $ $ 8,267 16,922 1,579 875 (8,724) 479 (180) (334) 3,140 19,609 (464) 18,778 9,878 30,750 (126,231) — (4,872) (1,500) (4,380) (96,355) 10,336 (1,799) — (102) 8,435 (69,142) 98,117 28,975 581 194 2,360 162 1,313 211 See accompanying notes to consolidated financial statements. 65                                                                               Notes to Consolidated Financial Statements 1. Description of Business and Summary of Significant Accounting Policies Description of Business A10 Networks, Inc. (together with our subsidiaries, the “Company”, “we”, “our” or “us”) was incorporated in California in 2004 and reincorporated in Delaware in March 2014. We are headquartered in San Jose, California and have wholly-owned subsidiaries throughout the world including Asia and Europe. We are a leading provider of secure application solutions and services that enable a new generation of intelligently connected companies with the ability to continuously improve cyber protection and digital responsiveness across dynamic Information Technology (“IT”) and network infrastructures. Our product portfolio seeks to address many of the aforementioned challenges and solution requirements. The portfolio consists of six secure application solutions; Thunder Application Delivery Controller (“ADC”), Lightning Application Delivery Controller (“Lightning ADC”), Thunder Carrier Grade Networking (“CGN”), Thunder Threat Protection System (“TPS”), Thunder SSL Insight (“SSLi”) and Thunder Convergent Firewall (“CFW”), and two intelligent management and automation tools; Harmony Controller and aGalaxy TPS. Our solutions are available in a variety of form factors, such as optimized hardware appliances, bare metal software, containerized software, virtual appliances and cloud-native software. Basis of Presentation The accompanying consolidated financial statements include those of A10 Networks, Inc. and its subsidiaries, and have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the United States Securities and Exchange Commission (the “SEC”). All intercompany accounts and transactions have been eliminated in consolidation. Reclassifications Certain prior year amounts have been reclassified to conform to current year presentation in the consolidated statements of cash flows. We have combined the line item “Accrued litigation expenses” into “Other” within net cash (used in) provided by operating activities. Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Those estimates and assumptions affect revenue recognition and deferred revenue, the allowance for doubtful accounts, the sales return reserve, the valuation of inventory, the fair value of marketable securities, contingencies and litigation, accrued liabilities, deferred commissions and the determination of fair value of stock-based compensation. These estimates are based on information available as of the date of the consolidated financial statements; therefore, actual results could differ from management’s estimates. Significant Accounting Policies Cash and Cash Equivalents Cash and cash equivalents include bank deposits and short-term, highly liquid investments purchased with an original maturity of 90 days or less. Our cash equivalents consist of money market funds. Marketable securities We classify our investments in debt securities as available-for-sale and record these investments at fair value. We may sell these investments at any time before their maturities. Accordingly, we classified our securities, including those with maturities exceeding twelve months, as current assets and included in marketable securities on the consolidated balance sheets. Unrealized gains and losses are reported in accumulated other comprehensive loss, net of taxes, in stockholders’ equity. Realized gains and losses are determined based on the specific identification method. Realized gains and losses and other-than- 66 temporary impairment charges, if any, on marketable securities are reported in interest and other income (expense), net as incurred in the consolidated statements of operations. We regularly review our investment portfolio to identify and evaluate investments that have indicators of possible impairment. Investments are considered impaired when a decline in fair value is judged to be other-than-temporary. If the cost of an individual investment exceeds its fair value, we evaluate, among other factors, general market conditions, the duration and extent to which the fair value is less than cost, and our intent and ability to hold the investment. Once a decline in fair value is determined to be other-than-temporary, we will record an impairment charge and establish a new cost basis in the investment. Fair Value Measurement Our financial instruments consist of cash, cash equivalents, marketable securities, accounts receivable and accounts payable. Our cash equivalents are measured and recorded at fair value on a recurring basis. Marketable securities are comprised of certificates of deposit, corporate securities, U.S. Treasury and agency securities, commercial paper and asset-backed securities and are measured at fair value on a recurring basis. Accounts receivable and accounts payable are stated at their carrying value, which approximates fair value due to the short time to the expected receipt or payment. Financial instruments recorded at fair value are measured and classified using the three-level valuation hierarchy as described below: Level 1 — observable inputs for identical assets or liabilities, such as quoted prices in active markets. Level 2 — inputs other than the quoted prices in active markets that are observable either directly or indirectly. Level 3 — unobservable inputs in which there is little or no market data, which requires us to develop our own assumptions when pricing the financial instruments. Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at invoice amounts, net of allowances for doubtful accounts. We evaluate the collectibility of our accounts receivable based on known collection risks and historical experience. In circumstances where we are aware of a specific customer’s inability to meet its financial obligations to us (for examples, bankruptcy filings or substantial downgrading of credit ratings), we record a specific reserve for bad debts against amounts due to reduce the net recognized receivable to the amount we reasonably believe will be collected. For all other customers, we record reserves for bad debts based on the length of time the receivables are past due and our historical experience of collections and write-offs. Inventory Inventory is stated at the lower of cost or net realizable value. Inventory cost is determined using first-in, first-out method. We evaluate inventory for excess and obsolete products, based on management’s assessment of future demand and market conditions. Inventory write-downs, once established, are not reversed as they establish a new cost basis for the inventory. Inventory write downs are included as a component of cost of products revenue in the consolidated statements of operations. Property and Equipment, Net Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets. Depreciation on property and equipment, excluding leasehold improvements, ranges from 1 to 3 years. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the assets or the remaining lease term. Amortization on leasehold improvements ranges from 2 to 8 years. Goodwill Goodwill represents the excess of purchase consideration over the fair values of assets acquired and liabilities assumed in a business combination. Goodwill is not amortized but is reviewed for possible impairment annually in the fourth quarter or more frequently if impairment indicators arise. We have identified a single reporting unit for the purpose of our goodwill impairment tests, and the fair value of our reporting unit has been determined by our enterprise value. We may elect to utilize a 67 qualitative assessment to determine whether it is more likely than not that the fair value of our reporting unit is less than its carrying value. If, after assessing the qualitative factors, we determine that it is more likely than not that the fair value of our reporting unit is less than its carrying value, an impairment analysis will be performed. We compare the fair value of our reporting unit with its carrying amount and if the carrying value of the reporting unit exceeds its fair value, an impairment loss will be recognized. We did not identify impairment of goodwill for any periods presented. Intangible Assets Intangible assets are recorded at fair value and amortized on a straight-line basis over their estimated useful lives, which range from 5 to 10 years. We did not have impairment of intangible assets during the years ended December 31, 2018 , 2017 and 2016 . Impairment of Long-Lived Assets We evaluate our property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of our long-lived assets may not be recoverable. Recoverability of an asset group is measured by comparison of its carrying amount to the expected future undiscounted cash flows that the asset group is expected to generate. If it is determined that an asset group is not recoverable, an impairment loss is recorded in the amount by which the carrying amount of the asset group exceeds its fair value. Revenue Recognition We recognize revenue when we transfer control of promised goods or services to our customers in an amount that reflects the consideration to which we expect to be entitled to in exchange for those goods or services. See Note 2 for further discussion on revenue. Research and Development Costs Research and development efforts are focused on new product development and on developing additional functionality for our existing products. These expenses consist of personnel costs, and to a lesser extent, prototype materials, depreciation and certain allocated facilities and information technology costs. We expense research and development costs as incurred. Stock-Based Compensation Stock-based compensation expense is measured on the grant date based on the fair value of the award and recognized on a straight-line basis over the requisite service period, reduced for actual forfeitures. The fair values of restricted stock units (“RSUs”) and performance-based restricted stock units (“PSUs”) are estimated using our stock price on the grant date. The fair value of options and employee stock purchase rights is estimated using the Black-Scholes model on the grant date. The Black-Scholes model determines the fair value of share-based payment awards based on assumptions including expected term, stock price volatility, and risk-free interest rate. The fair value of market-performance based restricted stock units (“MSUs”) is valued using the Monte Carlo simulation model, which uses the stock price, expected volatility and risk-free interest rate to determine the fair value. Warranty Costs Our appliance hardware and software generally carry a warranty period of 90 days. Estimates of future warranty costs are based on historical returns and the application of the historical return rates to our in-warranty installed base. Warranty costs to repair or replace items sold to customers have been insignificant for the years ended December 31, 2018 , 2017 and 2016 . Foreign Currency The functional currency of our foreign subsidiaries is the U.S. dollar. Transactions denominated in non-functional currencies are remeasured to the functional currency at the average exchange rate for the period. Non-functional currency monetary assets and liabilities are remeasured to the functional currency using the exchange rate in effect at the balance sheet date, and non-monetary assets and liabilities are remeasured at historical exchange rates. Gains and losses related to remeasurement are recorded in interest and other income (expense), net in the consolidated statements of operations. 68 Income Taxes We account for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in our consolidated financial statements or in our tax returns. Estimates and judgments occur in the calculation of certain tax liabilities and in the determination of the recoverability of certain deferred income tax assets, which arise from temporary differences and carryforwards. Deferred income tax assets and liabilities are measured using the currently enacted tax rates that apply to taxable income in effect for the years in which those tax assets are expected to be realized or settled. We regularly assess the likelihood that our deferred tax assets will be recovered from future taxable income and, to the extent we believe, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through an adjustment to income tax expense. The factors used to assess the likelihood of realization of our deferred tax assets include our forecast of future taxable income and available tax planning strategies that could be implemented to realize the net deferred tax assets. Assumptions represent our best estimates and involve inherent uncertainties and the application of our judgment. We account for uncertainty in income taxes recognized in our consolidated financial statements by regularly reviewing our tax positions and benefits to be realized. We recognize tax liabilities based upon our estimate of whether, and the extent to which, additional taxes will be due when such estimates are more- likely-than-not to be sustained. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained upon examination by taxing authorities. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. Advertising Costs Advertising costs are expensed when incurred. Advertising costs were $0.7 million ,  $0.6 million , and  $0.9 million  for the years ended  December 31, 2018 , 2017 and 2016 , respectively. Segment Information An operating segment is a component of an enterprise for which its discrete financial information is available and its operating results are regularly reviewed by chief operating decision maker for resource allocation decisions and performance assessment. Our chief operating decision maker is our Chief Executive Officer. Our Chief Executive Officer reviews financial information presented on a consolidated basis for purposes of allocating resources and assessing performance of the Company. Accordingly, we have one reportable segment and one operating segment. Vendor Business Concentration We rely on third parties to manufacture our hardware appliances and we purchase raw materials from third-party vendors. We outsourced substantially all of our manufacturing services to three independent manufacturers. In addition, we purchase certain strategic component inventory which is consigned to our third- party manufacturers. Other hardware components included in our products are sourced from various suppliers by our manufacturers and are principally industry standard parts and components that are available from multiple vendors. Concentration of Credit Risk and Significant Customers Financial instruments that potentially subject us to concentrations of credit risk consist of cash, cash equivalents, marketable securities and accounts receivable. Our cash, cash equivalents and marketable securities are held and invested in high-credit quality financial instruments by recognized financial institutions and are subject to minimum credit risk.  Our accounts receivable are unsecured and represent amounts due to us based on contractual obligations of our customers. We mitigate credit risk in respect to accounts receivable by performing periodic credit evaluations based on a number of factors, including past transaction experience, evaluation of credit history and review of the invoicing terms of the contract. We generally do not require our customers to provide collateral to support accounts receivable. Significant customers, including distribution channel partners and direct customers, are those which represent 10% or more of our total revenue for each period presented or our gross accounts receivable balance as of each respective balance sheet 69 date. Revenues from our significant customers as a percentage of our total revenue are as follows:  Customer A (a distribution channel partner) Customer B (a distribution channel partner) * represents less than 10% of total revenue Years Ended December 31, 2018 14% 10% 2017 * * 2016 * 14% As of December 31, 2018 , two customers accounted for 16% and 12% of our total gross accounts receivable. As of December 31, 2017 , no customer accounted for 10% or more of our total gross accounts receivable. Recently Adopted Accounting Guidance In May 2017, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting, to provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. This standard is effective for annual periods beginning after December 15, 2017 and interim periods within that reporting period. The amendments will be applied prospectively to an award modified on or after the adoption date. The adoption of ASU 2017-09 on January 1, 2018 did not impact our consolidated financial statements or disclosures. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), as subsequently amended, which supersedes the revenue recognition requirements in Accounting Standards Codification (“ASC”) Topic 605, Revenue Recognition. This ASU requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This ASU also includes Subtopic 340-40, Other Assets and Deferred Costs - Contracts with Customers, which requires the capitalization of incremental customer acquisition costs and amortization of these costs over the contract period or estimated customer life which resulted in the recognition of a deferred commission asset on our consolidated balance sheet. We adopted ASU 2014-09 and its related amendments (collectively “ASC 606”) on January 1, 2018 using the modified retrospective method. See Note 2 for disclosure on the impact of adopting this standard. In March 2018, the FASB issued ASU No. 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin (SAB) No. 118. These amendments add SEC guidance to the FASB Accounting Standards Codification regarding the Tax Cuts and Jobs Act pursuant to the issuance of SAB 118. The amendments are effective upon addition to the FASB Codification. See Note 9 in this report for disclosures related to the effect of the Tax Cuts and Jobs Act and our utilization of SAB 118. Recent Accounting Pronouncements Not Yet Effective In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), as amended, to supersede existing guidance on accounting for leases in Topic 840, Leases. Topic 842 generally requires lessees to recognize operating and financing lease liabilities and corresponding right-of-use assets on the balance sheet and to provide enhanced disclosures surrounding the amount, timing and uncertainty of cash flows arising from leasing arrangements. We will adopt the new standard effective January 1, 2019 on a modified retrospective basis, under which we will recognize the cumulative effects of initially applying the standard as an adjustment to the opening balance of accumulated deficit on the adoption date and will not restate comparative periods. We will elect the package of practical expedients permitted under the transition guidance, which allows us to carry-forward our historical lease classification and our assessment on whether a contract is or contains a lease. We will also elect to apply the hindsight practical expedient which allows us to use hindsight in determining the lease term. Additionally, we will elect to not apply the new standard’s recognition requirements to leases with an initial term of 12 months or less and instead to recognize lease payments in the consolidated statements of operations on a straight-line basis over the lease term. On the adoption date, we estimate we will recognize on our consolidated balance sheet approximately $5.9 million of right-of-use assets, $6.6 million of lease liabilities, and derecognize existing deferred rent of approximately $0.7 million . These are preliminary estimates that are subject to change as we finalize our adoption. 70                         Other than described above, we do not expect the new standard to have any other material impacts on our consolidated financial statements. There are several other new accounting pronouncements issued by the FASB, which we will adopt. However, we do not believe any of those accounting pronouncements will have a material impact on our consolidated financial position, operating results or statements of cash flows. 2 . Revenue ASC 606 Adoption Impact On January 1, 2018, we adopted ASC 606 applying the modified retrospective method. We recognized the cumulative effect of initially applying the new guidance as an adjustment to the opening balance of accumulated deficit as of the adoption date. We applied ASC 606 to all contracts that were not completed at the date of initial application. Comparative information for prior periods has not been restated and continues to be reported under the accounting standards in effect for those periods. In connection with the adoption of ASC 606, we also adopted ASC 340-40, Other Assets and Deferred Costs - Contracts with Customers, which requires the deferral of incremental costs of obtaining a contract with a customer. Collectively, we refer to ASC 606 and ASC 340-40 as the “new standard.” Adoption of the new standard resulted in changes to our accounting policies for revenue recognition, commissions expense and deferred commissions as discussed below. We recorded a reduction to opening accumulated deficit of  $12.4 million  as of January 1, 2018 due to the cumulative impact of adopting the new standard as follows: • • A decrease in total deferred revenue of  $4.0 million  primarily due to the removal of the limitation on contingent revenue that would have accelerated revenue recognition for certain of our historical revenue contracts; and Recognition of a deferred commissions asset of  $8.4 million on our consolidated balance sheet due to the requirement under the new standard to recognize incremental customer acquisition costs in our consolidated statement of operations as the related performance obligations are met as compared to the previous recognition to expense as incurred. Impact on the Consolidated Financial Statements The following tables summarize the impact of the new standard on our consolidated balance sheet and consolidated statement of operations for the period presented: Selected Consolidated Balance Sheet Line Items (in thousands) Assets Prepaid expenses and other current assets Other non-current assets Liabilities Deferred revenue, current Deferred revenue, non-current Stockholders' Equity Accumulated deficit As Reported December 31, 2018 Adjustments Increase (Decrease) Balance Without Adopting the New Standard 14,662   $ 8,620   63,874   34,092   (6,557)   $ (3,184)   3,390   3,204   8,105 5,436 67,264 37,296 (272,246)   (16,335)   (288,581) $ 71                                                                       Selected Consolidated Statement of Operations Line Items (in thousands, except per share amounts) Revenue - products Revenue - services Total revenue Gross profit Sales and marketing Total operating expenses Loss from operations Net loss Basic and diluted net loss per share Changes in Accounting Policies Revenue Recognition Year Ended December 31, 2018 As Reported Adjustments Increase (Decrease) Balance Without Adopting the New Standard $ 144,682   $ (2,594)   $ 87,541   232,223   180,327   103,214   208,006   (27,679)   (27,617)   (0.38)   —   (2,594)   (2,594)   1,345   1,345   (3,939)   (3,939)   142,088 87,541 229,629 177,733 104,559 209,351 (31,618) (31,556) (0.43) We derive revenue from two sources: (i) products revenue, which includes hardware, perpetual software license and subscription revenue; and (ii) services revenue, which includes post contract support (“PCS”), professional services, and training. A substantial portion of our revenue is from sales of our products and services through distribution channel partners, such as resellers and distributors. Revenue is recognized, net of applicable taxes, upon transfer of control of promised products or services to customers in an amount that reflects the consideration we expect to be entitled to receive in exchange for those products or services. We apply the following five-step revenue recognition model: • • • • • Identification of the contract, or contracts, with a customer Identification of the performance obligations in the contract Determination of the transaction price Allocation of the transaction price to the performance obligations in the contract Recognition of revenue when, or as, performance obligations are satisfied. PCS revenue includes arrangements for software support and technical support for our products. PCS is offered under renewable, fee-based contracts, which include technical support, hardware repair and replacement parts, bug fixes, patches, and unspecified upgrades on a when-and-if available basis. Revenue for PCS services is recognized on a straight-line basis over the service contract term, which is typically one year, but can be up to five years as there is no discernable pattern of transfer related to these promises. Billed but unearned PCS revenue is included in deferred revenue. Professional service revenue primarily   consists of the fees we earn related to installation and consulting services. We recognize revenue from professional services upon delivery or completion of performance. Professional service arrangements are typically short term in nature and are largely completed within 30 to 90 days from the start of service. Revenue is recognized for training when the training course is delivered. Contracts with Multiple Performance Obligations Most of our contracts with customers, other than renewals of PCS, contain multiple performance obligations with a combination of products and PCS. Products and PCS generally qualify as distinct performance obligations. Our hardware includes embedded ACOS software, which together deliver the essential functionality of our products. For contracts which contain multiple performance obligations, we allocate revenue to each distinct performance obligation based on the standalone selling price (“SSP”). Judgment is required to determine the SSP for each distinct performance obligation. We use a range of 72                               amounts to estimate SSP for products and PCS sold together in a contract to determine whether there is a discount to be allocated based on the relative SSP of the various products and PCS. If we do not have an observable SSP, such as when we do not sell a product or service separately, then SSP is estimated using judgment and considering all reasonably available information such as market conditions and information about the size and/or purchase volume of the customer. We generally use a range of amounts to estimate SSP for individual products and services based on multiple factors including, but not limited to the sales channel (reseller, distributor or end customer), the geographies in which our products and services are sold, and the size of the end customer. We account for multiple contracts with a single partner as one arrangement if the contractual terms and/or substance of those agreements indicate that they may be so closely related that they are, in effect, parts of a single contract. We may occasionally accept returns to address customer satisfaction issues even though there is generally no contractual provision for such returns. We estimate returns for sales to customers based on historical returns rates applied against current-period shipments. Specific customer returns and allowances are considered when determining our sales return reserve estimate. Our policy applies to the accounting for individual contracts. However, we have elected a practical expedient to apply the guidance to a portfolio of contracts or performance obligations with similar characteristics so long as such application would not differ materially from applying the guidance to the individual contracts (or performance obligations) within that portfolio. Consequently, we have chosen to apply the portfolio approach when possible, which we do not believe will happen frequently. Additionally, we will evaluate a portfolio of data, when possible, in various situations, including accounting for commissions, rights of return and transactions with variable consideration. We report revenue net of sales taxes. We include shipping charges billed to customers in revenue and the related shipping costs are included in cost of product revenue. Contract Balances The following table reflects contract balances with customers (in thousands): Balance Sheet Line Reference Accounts receivables, net Deferred revenue, current Deferred revenue, non-current As of As of Adoption December 31, 2018 January 1, 2018   $ 53,972   $ 63,874   34,092   48,266 59,360 31,276 We receive payments from customers based upon billing cycles. Invoice payment terms are usually ranging from 30 to 90 days. Accounts receivable are recorded when the right to consideration becomes unconditional. Contract assets include amounts related to our contractual right to consideration for performance obligations not yet billed and are included in prepaid and other current assets in the consolidated balance sheets. The contract assets amount is immaterial as of December 31, 2018 and as of the adoption date. Deferred revenue primarily consists of amounts that have been invoiced but not yet been recognized as revenue and consists of performance obligations pertaining to support and subscription services. During the year ended December 31, 2018 , we recognized revenue of $60.2 million related to deferred revenues at the beginning of the period. 73               Deferred revenue consisted of the following (in thousands): Deferred revenue: Products Services Total deferred revenue Less: current portion Non-current portion Deferred Contract Acquisition Costs December 31, 2018 December 31, 2017 $ $ 5,216   $ 92,750   97,966   (63,874)   34,092   $ 6,161 88,476 94,637 (61,858) 32,779 In connection with the adoption of ASC 340-40, we capitalize certain contract acquisition costs consisting of incremental sales commissions incurred to obtain customer contracts. Deferred commissions related to product revenues are recognized upon transfer of control to customers. Deferred commissions related to services revenue are recognized as the related performance obligations are met. Deferred commissions that will be recognized during the succeeding 12-month period are recorded as prepaid expenses and other current assets, and the remaining portion is recorded as other non-current assets. Amortization of deferred commissions is included in sales and marketing expense. As of December 31, 2018 , current and non-current portions of deferred contract acquisition costs were $6.6 million and $3.2 million , respectively, and the related amortization amount was $4.9 million for 2018. We had  no  impairment loss in relation to the costs capitalized and no asset impairment charges related to contract assets. Remaining Performance Obligations Remaining performance obligations represent contracted revenues that are non-cancellable and have not yet been recognized due to unsatisfied or partially satisfied performance obligations, which includes deferred revenues and amounts that will be invoiced and recognized as revenues in future periods. We expect to recognize revenue on the remaining performance obligations as follows (in thousands): Within 1 year Next 2 to 3 years Thereafter Total 74 December 31, 2018 63,874 27,678 6,414 97,966 $ $                                   3. Marketable Securities and Fair Value Measurements Marketable Securities Marketable securities, classified as available-for-sale, consisted of the following (in thousands): Certificates of deposit   $ Corporate securities U.S. Treasury and agency securities Commercial paper Asset-backed securities Amortized Cost 11,000   $ 46,442   1,748   12,327   16,381   December 31, 2018 Gross Unrealized Gains Gross Unrealized Losses Fair Value December 31, 2017 Amortized Cost 17,000   $ Gross Unrealized Gains 7   $ 11   —   1   5   (3)   $ 11,004   $ (116)   46,337   39,154   (12)   (5)   (32)   1,736   12,323   16,354   5,744   9,225   13,567   Gross Unrealized Losses (1)   $ Fair Value 17,005 (76)   39,079 (19)   (2)   (33)   5,725 9,224 13,534 84,567 6   $ 1   —   1   —   Total   $ 87,898   $ 24   $ (168)   $ 87,754   $ 84,690   $ 8   $ (131)   $ During the years ended December 31, 2018 and 2017 , we did not reclassify any amount to earnings from accumulated other comprehensive loss related to unrealized gains or losses. The following table summarizes the cost and estimated fair value of marketable securities based on stated effective maturities as of December 31, 2018 (in thousands): Less than 1 year Mature in 1 - 3 years Total Amortized Cost Fair Value $ $ 61,153   $ 26,745   87,898   $ 61,042 26,712 87,754 All available-for-sale securities have been classified as current because they are available for use in current operations. Marketable securities in an unrealized loss position consisted of the following (in thousands): As of December 31, 2018 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Less Than 12 Months 12 Months or More Total Certificates of deposit $ Corporate securities U.S. Treasury and agency securities Commercial paper Asset-backed securities 2,997   $ 29,435   992   9,888   8,499   Total $ 51,811   $ (3) (68) (7) (5) (15) (98) $ —   $ 7,601   744   —   4,758   $ 13,103   $ —   $ (48) 2,997   $ 37,036   (5) —   (17) (70) 1,736   9,888   13,257   $ 64,914   $ (3) (116) (12) (5) (32) (168) 75                                                                                                                                       As of December 31, 2017 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Less Than 12 Months 12 Months or More Total Certificates of deposit $ Corporate securities U.S. Treasury and agency securities Commercial paper Asset-backed securities 2,999   $ 36,079   2,246   4,232   11,415   (1)   $ (74)   —   $ 1,499   —   $ (2) 2,999   $ 37,578   (2)   (2)   (32)   3,479   —   728   (17) —   (1) (20) 5,725   4,232   12,143   (1) (76) (19) (2) (33) Total $ 56,971   $ (111)   $ 5,706   $ $ 62,677   $ (131) Based on evaluation of securities that have been in a continuous loss position, we determined the gross unrealized losses on our marketable securities as of December 31, 2018 were temporary in nature and related primarily to interest rate shifts rather than changes in the underlying credit quality of the securities we hold. As we have the ability to hold these investments until maturity, or for the foreseeable future, no decline was deemed to be other-than-temporary. Fair Value Measurements The following is a summary of our cash, cash equivalents and marketable securities measured at fair value on a recurring basis (in thousands): December 31, 2018 December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash Cash equivalents Certificates of deposit Corporate securities U.S. Treasury and agency securities Commercial paper Asset-backed securities   $ 39,113   $ 1,508   —   $ —   —   —   —   —   —   11,004   46,337   1,736   12,323   16,354   —   $ 39,113   $ 34,453   $ —   —   —   —   —   —   1,508   11,004   46,337   1,736   12,323   16,354   12,114   —   —   —   —   —   —   $ —   17,005   39,079   5,725   9,224   13,534   —   $ —   —   —   —   —   —   34,453 12,114 17,005 39,079 5,725 9,224 13,534 Total   $ 40,621   $ 87,754   $ —   $ 128,375   $ 46,567   $ 84,567   $ —   $ 131,134 There were no transfers between Level 1 and Level 2 fair value measurement categories during the years ended December 31, 2018 and 2017 . 4. Other Balance Sheet Accounts Details Allowance for Doubtful Accounts The following table presents the changes in the allowance for doubtful accounts (in thousands): Allowance for doubtful accounts, beginning balance Increase (decrease) of provision Write-offs Allowance for doubtful accounts, ending balance 76 December 31, 2018 December 31, 2017 $ $ 983 (26) (638) 319 $ $ 1,920 364 (1,301) 983                                                                                                                                         Inventory Inventory consisted of the following (in thousands): Raw materials Finished goods Total inventory Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following (in thousands): Prepaid expenses Deferred contract acquisition costs Other Prepaid expenses and other current assets Property and Equipment, Net Property and equipment, net, consisted of the following (in thousands): Equipment Software Furniture and fixtures Leasehold improvements Construction in progress Property and equipment, gross Less: accumulated depreciation Property and equipment, net December 31, 2018 December 31, 2017 7,979   $ 9,951   17,930   $ 6,643 10,934 17,577 December 31, 2018 December 31, 2017 6,679   $ 6,564   1,419   14,662   $ 5,768 — 1,057 6,825 $ $ $ $ Useful Life (in years) 1-3 1-3 1-3 2-8 December 31, 2018 December 31, 2017 $ 49,804   $ 4,088   967   3,832   160   58,851   (51,589)   $ 7,262   $ 47,817 3,988 950 3,824 — 56,579 (46,666) 9,913 Depreciation expense on property and equipment was $6.4 million , $7.1 million and $7.6 million for the years ended December 31, 2018 , 2017 and 2016 , respectively. Intangible Assets Purchased intangible assets, net, consisted of the following (in thousands): Developed technology Patents Total Cost 5,050   $ 2,936   7,986   $ $ $ December 31, 2018 Accumulated Amortization Net Cost December 31, 2017 Accumulated Amortization (2,525)   $ (1,713)   (4,238)   $ 2,525   $ 1,223   3,748   $ 5,050   $ 2,936   7,986   $ (1,515)   $ (1,281)   (2,796)   $ Net 3,535 1,655 5,190 77                                                                                                                   Amortization expense related to purchased intangible assets was $1.4 million , $1.4 million and $0.7 million for the years ended December 31, 2018 , 2017 and 2016 . Purchased intangible assets will be amortized over a remaining weighted average useful life of 2.6 years. Future amortization expense for purchased intangible assets as of December 31, 2018 is as follows (in thousands): Fiscal Year 2019 2020 2021 Total Accrued Liabilities Accrued liabilities consisted of the following (in thousands): Accrued compensation and benefits Accrued tax liabilities Other Total accrued liabilities 5. Credit Facility $ $ 1,443 1,442 863 3,748 December 31, 2018 December 31, 2017 $ $ 15,283   $ 4,455   5,553   25,291   $ 13,828 2,985 5,022 21,835 In November 2016, we entered into a loan and security agreement (the “2016 Credit Facility”) with Silicon Valley Bank (“SVB”) as the lender. The 2016 Credit Facility provides a three -year, $25.0 million revolving credit facility, which includes a maximum of $25.0 million letter of credit subfacility. When the balance of our cash, cash equivalents and marketable securities minus outstanding revolving loans and letters of credit equals or exceeds  $50.0 million , loans may be advanced under the 2016 Credit Facility up to the full  $25.0 million . When our net cash falls below  $50.0 million , loans may be advanced under the 2016 Credit Facility based on a borrowing base equal to a specified percentage of the value of our eligible accounts receivable. The loans bear interest, at our option, at (i) the prime rate reported in The Wall Street Journal, minus 0.50% or (ii) a LIBOR rate determined in accordance with the 2016 Credit Facility, plus 2.50% . We are required to pay customary closing fees, commitment fees and letter of credit fees for a facility of this size and type. In September 2018, we entered into an amendment with SVB to reduce the unused revolving credit facility fee on the 2016 Credit Facility from 0.4% to 0.3% . Our obligations under the 2016 Credit Facility are secured by substantially all of our assets, excluding our intellectual property. The 2016 Credit Facility contains customary affirmative and negative covenants. In addition, the 2016 Credit Facility requires us to maintain compliance with an adjusted quick ratio of not less than 1.50 :1.00, as determined in accordance with the 2016 Credit Facility. The 2016 Credit Facility also restricts our ability to pay cash dividends or make other distributions on our capital stock. As of December 31, 2018 , we had no outstanding balance under the 2016 Credit Facility and were in compliance with all facility covenants. 78                             6. Commitments and Contingencies Legal Proceedings Litigation From time to time, we may be party or subject to various legal proceedings and claims, either asserted or unasserted, which arise in the ordinary course of business. Some of these proceedings involve claims that are subject to substantial uncertainties and unascertainable damages. We make a provision for a liability when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Unless otherwise specifically disclosed in this note, we have determined that no provision for liability nor disclosure is required related to any claim against us because: (a) there is not a reasonable possibility that a loss exceeding amounts already recognized (if any) may be incurred with respect to such claim; (b) a reasonably possible loss or range of loss cannot be estimated; or (c) such estimate is immaterial. On March 22, 2018, the Company, our Chief Executive Officer, our Chief Financial Officer, and certain former officers, were named as defendants in a putative class action lawsuit filed in the United States District Court for the Northern District of California, captioned Shah v. A10 Networks, Inc. et al., 3:18-cv- 01772-VC (the “Securities Action”). On August 31, 2018, the court appointed a lead plaintiff. On October 5, 2018, the lead plaintiff filed an amended complaint which asserted claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5 promulgated thereunder. The amended complaint named the same defendants as the initial complaint, in addition to one of the Company’s former executive vice presidents. The Company and individual defendants filed motions to dismiss the amended complaint. On February 21, 2019, the court granted the motions to dismiss with leave to amend within 21 days . The lead plaintiff did not file an amended complaint by the Court-ordered deadline. On May 30, 2018, certain of our current and former directors and officers were named as defendants in a putative shareholder derivative lawsuit filed in the United States District Court for the Northern District of California, captioned Moulton v. Chen et al., 3:18-cv-03223-VC (the “Derivative Action”). We were also named as a nominal defendant. The complaint in the Derivative Action alleges breaches of fiduciary duties and other related claims in connection with purported misrepresentations related to internal controls and revenues and failures to ensure that financial statements were made in accordance with generally accepted accounting principles. Plaintiff seeks unspecified damages allegedly sustained by the Company, restitution, and other relief. On July 11, 2018 the Derivative Action was stayed until a motion to dismiss in the Securities Action is granted with prejudice or denied in whole or in part. Defendants are not required to move or otherwise respond to the current complaint. On October 24, 2018, the Company was sued in the Federal District Court for the Northern District of California by FireNet Technologies, LLC, which we believe is a non-practicing patent holding company. The complaint alleged infringement of certain patents purportedly owned by the plaintiff. In January 2019, we entered into a settlement agreement whereby we obtained a fully-paid up license and the case was dismissed with prejudice on February 4, 2019. Investigations The U.S. Securities and Exchange Commission (“SEC”) is conducting a private investigation into possible violations of Section 17(a) of the Securities Act of 1933 and Sections 10(b), 13(a), and 13(b) of the Securities Exchange Act of 1934 (“Exchange Act”) and Rules 10b-5, 12b-20, 13a-1, 13a-11, 13a-13, 13a- 14, 13a-15, and 13b2-1 thereunder.  The Company is cooperating with the SEC regarding this investigation. The Company is unable to predict the duration, scope or outcome of the investigation, but an adverse outcome is reasonably possible. In such an event, the Company could be required to pay fines and sanctions and/or implement additional remedial measures. However, the Company is not able to estimate the likelihood or a reasonable range of possible loss. Lease and Other Commitments We lease various operating spaces in the United States, Asia and Europe under non-cancelable operating lease arrangements that expire on various dates through April 2022 . These arrangements require us to pay certain operating expenses, such as taxes, repairs and insurance, and contain renewal and escalation clauses. We recognize rent expense under these arrangements on a straight-line basis over the term of the lease. 79 We have open purchase commitments with third-party contract manufacturers with facilities in Taiwan to supply nearly all of our finished goods inventories, spare parts, and accessories. These purchase orders are expected to be paid within one year of the issuance date. The following table summarizes our non-cancelable operating leases and unconditional purchase obligations as of  December 31, 2018 (in thousands): Years Ending December 31, 2019 2020 2021 2022 2023 Total Operating Leases and Other Contractual Obligation (1) 3,907   1,921   1,194   313   —   Purchase Commitments   19,296   $ $ Total —   —   —   —   7,335   $ 19,296   $ $ $ 23,203 1,921 1,194 313 — 26,631 (1) Other contractual obligation represents the technology licensing arrangement we entered into in 2008 over the life of the associated patents. The last annual payment of $140 thousand is due in January 2019. Rent expense was $4.5 million , $4.1 million and $3.5 million for the years ended December 31, 2018 , 2017 and 2016 , respectively. Guarantees and Indemnifications In the normal course of business, we provide indemnifications to customers against claims of intellectual property infringement made by third parties arising from the use of our products. Other guarantees or indemnification arrangements include guarantees of product and service performance, and standby letters of credit for lease facilities and corporate credit cards. We have not recorded a liability related to these indemnification and guarantee provisions and our guarantees and indemnification arrangements have not had any significant impact on our consolidated financial statements to date. 7. Equity Incentive Plans and Stock-Based Compensation Equity Incentive Plans 2014 Equity Incentive Plan The 2014 Equity Incentive Plan (the “2014 Plan”) provides for the granting of stock options, restricted stock awards, restricted stock units (“RSUs”), performance-based RSUs (“PSUs”), stock appreciation rights, performance units and performance shares to our employees, consultants and members of our board of directors. In June 2015, our board of directors adopted and our stockholders approved an amendment and restatement of the 2014 Plan, which increased the number of shares available for issuance under the 2014 Plan by the number of shares granted under the 2008 Stock Plan (the “2008 Plan”) that were or may in the future be canceled or otherwise forfeited or repurchased after March 20, 2014. As of December 31, 2018 , we had a total of 8,841,016 shares available for future grant. The shares authorized for the 2014 Plan increase annually by the least of (i)  8,000,000 shares, (ii)  5% of the outstanding shares of common stock on the last day of our immediately preceding fiscal year, or (iii) such other amount as determined by our Board of Directors. Accordingly, on January 1, 2019 , the number of shares in the 2014 Plan increased by 3,715,060 shares, representing 5% of the prior year end’s common stock outstanding. To date, we have granted stock options, RSUs and PSUs under the 2014 Plan. Stock options expire no more than 10 years  from the grant date and generally vest over four years. In the case of an incentive stock option granted to an employee, who at the time of grant, owns stock representing more than 10% of the total combined voting power of all classes of stock, the 80                   per share exercise price will be no less than  110%  of the fair market value per share on the date of grant, and the incentive stock option will expire no later than five years from the date of grant. For incentive stock options granted to any other employees and nonstatutory stock options granted to employees, consultants, or members of our board of directors, the per share exercise price will be no less than 100% of the fair market value per share on the date of grant. RSUs and PSUs generally vest from one to four years. 2014 Employee Stock Purchase Plan The 2014 Employee Stock Purchase Plan (the “2014 Purchase Plan”) was suspended effective March 16, 2018 due to the delay of the Form 10-K filing for the year ended December 31, 2017. In October 2018, the Board approved amending the 2014 Purchase Plan (the “Amended 2014 Purchase Plan”) in order to, among other things, reduce the maximum contribution participants can make under the plan from 15% to 10% of eligible compensation. The Amended 2014 Purchased Plan also reflects revised offering periods, which were changed from 24 months to six months in duration and that begin on or about December 1 and June 1 each year, starting in December 2018. The Amended 2014 Purchase Plan permits eligible employees to purchase shares of our common stock through payroll deductions with up to 10% of their pre-tax eligible earnings subject to certain Internal Revenue Code limitations. The purchase price of the shares is  85%  of the lower of the fair market value of our common stock on the first day of a six-month offering period or the relevant purchase date. In addition, no participant may purchase more than  1,500  shares of common stock in each purchase period. As of December 31, 2018 , we had 3,065,182 shares available for future issuance under the Amended 2014 Purchase Plan. During 2018, there was no stock purchased by employees under the Amended 2014 Purchase Plan or the 2014 Purchase Plan. Stock-Based Compensation A summary of our stock-based compensation expense is as follows (in thousands): Stock-based compensation by type of award: Stock options Stock awards Employee stock purchase rights (1) Total Stock-based compensation by category of expense: Cost of revenue Sales and marketing Research and development General and administrative Total Years Ended December 31, 2018 2017 2016 $ $ $ $ 1,353   $ 2,705   $ 10,445   5,240   11,421   3,077   17,038   $ 17,203   $ 1,602   $ 1,362   $ 5,667   6,631   3,138   6,075   6,343   3,423   17,038   $ 17,203   $ 4,153 12,567 202 16,922 1,105 7,006 5,732 3,079 16,922 (1) Amount for the year ended December 31, 2018 includes $4.1 million of accelerated stock-based compensation expense. In March 2018, as a result of a suspension of the 2014 Purchase Plan due to our non-timely filing status, all unrecognized stock-based compensation expense related to ESPP under the 2014 Purchase Plan was accelerated and recognized within the consolidated statement of operations. As of December 31, 2018 , we had $33.0 million of unrecognized stock-based compensation expense related to unvested stock-based awards, including ESPP under our Amended 2014 Purchase Plan, which will be recognized over a weighted-average period of  2.5 years. 81                                                       Fair Value Determination: The fair values of stock options and employee stock purchase rights were estimated as of the grant date using the Black-Scholes option-pricing model with the following assumptions:  Expected term (in years) Risk-free interest rate Expected volatility Dividend rate Stock Options Years Ended December 31, Employee Stock Purchase Rights Years Ended December 31, 2018 4.8 3.1% 37% —% 2017 4.7 2.0% 43% —% 2016 4.9 1.4% 49% —% 2018 0.5 2.6% 28% —% 2017 1.3 1.4% 39% —% 2016 1.3 0.8% 42% —% • • • • Expected Term . We estimate the expected life of options based on an analysis of our historical experience of employee exercise and post-vesting termination behavior considered in relation to the contractual life of the option. The expected term for the employee stock purchase rights is based on the term of the purchase period. Risk-Free Interest Rate . The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant for zero coupon U.S. Treasury notes with maturities approximately equal to the expected terms of stock options and the employee stock purchase rights. Expected Volatility . For stock options, due to the limited trading history of our own common stock, we determined the share price volatility factor based on a combination of the historical volatility of our own common stock and the historical volatility of our peer group for the stock options. For employee stock purchase rights, we used the historical volatility of our own common stock. Dividend Rate . The expected dividend was assumed to be zero as we have never paid dividends and do not anticipate paying any dividends in the foreseeable future. Stock Options The following tables summarize our stock option activities and related information: Outstanding as of December 31, 2017 Granted Exercised Canceled Outstanding as of December 31, 2018 Vested and exercisable as of December 31, 2018 Number of Shares (thousands) Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (1) (thousands) 6,018 317 (1,029) (632) 4,674 4,062   $   $   $   $   $   $ 5.18     5.93   3.60   8.05   5.19   5.01   5.0 4.4   $   $ 7,395 7,188 (1) The aggregate intrinsic value represents the excess of the closing price of our common stock of  $6.24  as of December 31, 2018 over the exercise price of the outstanding in-the-money options. 82                                                                                                           Following is additional information pertaining to our stock option activities (in thousands, except per share data): Weighted-average grant date fair value of options granted (per share) Intrinsic value of options exercised (1) Years Ended December 31, 2018 2017 2016 $ $ 2.19   2,629   $ $ 3.14   8,013   $ $ 2.38 5,990 (1) Intrinsic value of options exercised is the difference between the closing price of our common stock at the time of exercise and the exercise price paid. Stock Awards We have granted RSUs to our employees, consultants and members of our board of directors, and PSUs and market performance-based restricted stock units (“MSUs”) to certain executives. In 2014 and 2015, we granted  540,000  MSUs and  40,000  MSUs, respectively, to certain executives. These MSUs will vest if the closing price of our common stock remains above certain predetermined target prices for  20  consecutive trading days within a  4 -year period following the grant date, subject to continued service by the award holder. As of December 31, 2018 , none of these MSUs were vested and all MSUs granted in 2014 expired. In February 2016, we granted  547,000  PSUs with certain financial and operational targets. Actual performance, as measured at the time and prior to the restatement of the 2016 financial statements, resulted in participants achieving 80%  of target. Given the PSUs did not contain explicit or implicit claw back rights, there was no change to stock-based compensation expense for the impact of the previously disclosed restatement of the 2016 consolidated financial statements. As of December 31, 2018 , 178,402 shares had vested, 181,598 shares had been forfeited, and the remaining shares will vest (as to 80% ) in annual tranches through February 2020 subject to continued service vesting requirements. In October 2016, we granted  60,641  PSUs with certain financial and operational targets. To the extent they become eligible to vest upon achievement of the performance targets, these PSUs additionally are subject to service condition vesting requirements with scheduled vesting dates of March 2017 through June 2018. As of December 31, 2018 , 30,320 shares were vested and 30,321 shares were forfeited. In October 2018, we granted 464,888 PSUs with certain financial targets. These PSUs will become eligible to vest at 75% upon the achievement of the performance targets by December 31, 2020, and are subject to service condition vesting requirements. The remaining 25% of these PSUs will become eligible to vest on the first anniversary of the initial vesting date. None of these PSUs were vested as of December 31, 2018. The following table summarizes our stock award activities and related information: Nonvested as of December 31, 2017 Granted Released Canceled Nonvested as of December 31, 2018 Number of Shares (thousands) Weighted-Average Grant Date Fair Value Weighted-Average Remaining Vesting Term (years) 5,568 3,568 (1,580) (1,582) 5,974 $ $ $ $ $ 6.88   5.95   7.04   6.03   6.51   1.6 83                                             Following is additional information pertaining to our RSU activities (in thousands, except per share data): Weighted-average grant date fair value of stock awards granted (per share) Total fair value of stock awards released (vested) during the period $ $ 5.95   $ 9,714   $ 8.55   $ 13,961   $ 6.50 9,687 Years Ended December 31, 2018 2017 2016 Stock Repurchase Program On October 23, 2017, our board of directors authorized a share repurchase program for up to $20.0 million of our common stock over 12 months.  No shares were repurchased under this program through its expiration in October 2018. 8. Net Loss Per Share Basic net loss per share is computed using the weighted average number of common shares outstanding for the period. Diluted net loss per share is computed using the weighted average number of common shares outstanding for the period plus potential dilutive common shares, including stock options, RSUs and employee stock purchase rights, unless the potential common shares are anti-dilutive. Since we had net losses in the years ended December 31, 2018 , 2017 and 2016 , none of the potential dilutive common shares were included in the computation of diluted shares for these periods, as inclusion of such shares would have been anti-dilutive.  The following table presents common shares related to potentially dilutive shares excluded from the calculation of diluted net loss per share as their effect would have been anti-dilutive (in thousands): Stock options, RSUs and employee stock purchase rights Common stock subject to repurchase Total 9. Income Taxes The geographical breakdown of loss before income taxes is as follows (in thousands): Years Ended December 31, 2018 2017 2016 9,621   —   9,621   12,184   —   12,184   13,631 14 13,645 Domestic loss Foreign income Loss before income taxes Years Ended December 31, 2018 2017 2016 $ $ (29,658)   $ (13,752)   $ 3,123   4,207   (26,535)   $ (9,545)   $ (24,429) 2,795 (21,634) 84                                               The provision for income taxes consists of the following (in thousands): Current provision for income taxes:   State   Foreign Total current Deferred tax expense (benefit):   Federal   Foreign Total deferred Provision for income taxes Years Ended December 31, 2018 2017 2016 44   $ 48   $ 953   997   (13)   98   85   1,023   1,071   26   109   135   1,082   $ 1,206   $ 41 1,009 1,050 17 (310) (293) 757 $ $ The reconciliation of the statutory federal income tax and the provision for income tax is as follows (in thousands, except percentages). The amounts disclosed as “Federal tax credits - net of uncertain tax positions” and “Non-deductible meals and entertainment expenses” for 2017 and 2016 were included in “Changes in federal valuation allowance” and “Other permanent items,” respectively, as previously reported. Such line items have been separately presented to correct errors in the above disclosures and to conform to the current year presentation. We assessed the significance of the misclassifications and concluded that they were not material to any prior periods. These corrections had no effect on our Consolidated Statements of Operations. 2018 2017 2016 Amount Percentage Amount Percentage Amount Percentage Years Ended December 31, Tax at statutory rate $ (5,572)   21.0 %   $ (3,245)   34.0 %   $ (7,356)   34.0 % State tax - net of federal benefits Foreign rate differential Changes in federal valuation allowance Change in federal tax rate due to Tax Cuts and Jobs Act Stock-based compensation Non-deductible meals and entertainment expenses Other permanent items 39   258   6,430   —   1,950   342   351   Federal tax credits - net of uncertain tax position (2,634)   Expenses for uncertain tax positions Other 137   (219)   (0.1) (1.0) (24.2) —   (7.3) (1.3) (1.3) 9.9 (0.5) 0.7 32   (655)   (21,038)   28,185   (1,169)   243   104   (1,634)   311   72   (0.3) 6.9 220.4 (295.3) 12.2 (2.5) (1.1) 17.1 (3.3) (0.7) Provision for income taxes $ 1,082   (4.1)%   $ 1,206   (12.6)%   $ 27   (666)   9,501   —   88   266   317   (1,875)   358   97   757   (0.1) 3.1 (44.0) — (0.4) (1.2) (1.5) 8.7 (1.7) (0.4) (3.5)% 85                                                                                                                           The tax effects of temporary differences that give rise to significant portions of deferred tax assets (liabilities) are as follows (in thousands): December 31, 2018 December 31, 2017 Deferred tax assets: Net operating loss carryforwards Research and development credits, net of uncertain tax positions $ Accruals, reserves, and other Stock-based compensation Depreciation and amortization Gross deferred tax assets Valuation allowance Total deferred tax assets Deferred tax liabilities: Deferred contract acquisition costs Other Total deferred tax liabilities Net deferred tax assets $ 43,869 22,051 11,264 2,628 1,952 81,764 (78,681) 3,083 (2,256) (13) (2,269) $ 814 $ 37,326 17,119 13,992 2,994 1,954 73,385 (72,458) 927 — (28) (28) 899 Recognition of deferred tax assets is appropriate when realization of these assets is more likely than not. Based upon the weight of available evidence, which includes our historical operating performance and the recorded cumulative net losses in prior fiscal periods, we recorded a full valuation allowance of $78.7 million and $72.5 million against the U.S. net deferred tax assets as of December 31, 2018 and 2017 , respectively. For the years ended December 31, 2018 and 2017 , the valuation allowance increased by $6.2 million and decreased by $15.6 million , respectively. As of December 31, 2018 and 2017 , we had U.S. federal net operating loss carryforwards of $185.0 million and $152.3 million , respectively, and state net operating loss carryforwards of $75.3 million and $73.6 million , respectively. The federal net operating loss carryforwards will expire at various dates beginning in the year ending December 31, 2025 , if not utilized. The state net operating losses expire in various years ending between 2019 and 2038 , if not utilized. Additionally, as of December 31, 2018 and 2017 , we had U.S. federal research and development credit carryforwards of $13.3 million and $10.3 million , and state research and development credit carryforwards of $14.2 million and $10.9 million , respectively. The federal credit carryforwards will begin to expire at various dates beginning in 2025 while the state credit carryforwards can be carried over indefinitely . Utilization of the net operating losses and credit carryforwards may be subject to an annual limitation provided for in the Internal Revenue Code Section 382 and similar state codes. Any annual limitation could result in the expiration of net operating loss and credit carryforwards before utilization. With respect to our undistributed foreign subsidiaries’ earnings we consider those earnings to be indefinitely reinvested and, accordingly, no related provision for U.S. federal and state income taxes has been provided. Our intention has not changed subsequent to the one-time transition tax under the Tax Act. Upon distribution of those earnings in the form of dividends or otherwise, we may be subject to both U.S. income taxes subject to an adjustment for foreign tax credits and withholding taxes in the various countries. As of December 31, 2018 and 2017 , the undistributed earnings approximated $10.8 million and $8.4 million , respectively. Our undistributed earnings through December 31, 2017 have been taxed under the one-time transition tax under the Tax Act. Uncertain Tax Positions As of December 31, 2018 , 2017 and 2016 , we had gross unrecognized tax benefits of $4.2 million , $3.8 million and $3.4 million , respectively. Accrued interest expense related to unrecognized tax benefits is recognized as part of our income tax provision in our consolidated statements of operations and is immaterial for the year ended December 31, 2018. Our policy for classifying interest and penalties associated with unrecognized income tax benefits is to include such items in income tax expense. 86                                                 The activity related to the unrecognized tax benefits is as follows (in thousands): Gross unrecognized tax benefits—beginning balance Increases (decrease) related to tax positions from prior years Increases related to tax positions taken during current year Decreases related to tax positions taken during the current year Gross unrecognized tax benefits—ending balance Years Ended December 31, 2018 2017 2016 3,782   $ 3,360   $ (266)   675   —   (151)   573   —   4,191   $ 3,782   $ 2,552 66 742 — 3,360 $ $ These amounts are related to certain deferred tax assets with a corresponding valuation allowance. As of December 31, 2018 , the total amount of unrecognized tax benefits, if recognized, that would affect the effective tax rate is $1.1 million . We do not anticipate a material change to our unrecognized tax benefits over the next twelve months. Unrecognized tax benefits may change during the next twelve months for items that arise in the ordinary course of business. We are subject to taxation in the United States, various states, and several foreign jurisdictions. Because we have net operating loss and credit carryforwards, there are open statutes of limitations in which federal, state and foreign taxing authorities may examine our tax returns for all years from 2005 through the current period. We are not currently under examination by any taxing authorities. The Tax Cuts and Jobs Act On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act makes broad and complex changes to the U.S. tax code including, but not limited to: (1) reducing the U.S. federal corporate tax rate from 35 percent to 21 percent; (2) generally eliminating U.S. federal income taxes on dividends from foreign subsidiaries; (3) requiring a current inclusion in U.S. federal taxable income of certain earnings of controlled foreign corporations; (4) eliminating the corporate alternative minimum tax (“AMT”) and changing how existing AMT credits can be realized; (5) creating the base erosion anti-abuse tax, a new minimum tax; (6) creating a new limitation on deductible interest expense; and (7) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017. On December 22, 2017, the SEC issued SAB 118, which provides guidance on accounting for the income tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting relating to the Tax Act under Accounting Standards Codification Topic 740, “Income Taxes” (“ASC 740”). In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Act for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for Tax Act-related income tax effects is incomplete, but the company is able to determine a reasonable estimate, it must record a provisional estimate in its financial statements. If a company cannot determine a provisional estimate to be included in its financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Act. We have completed our analysis of the Tax Act’s income tax effects. In accordance with SAB 118, the Tax Act-related income tax effects that we initially reported as provisional estimates were refined as additional analysis was performed. We have elected to account for Global Intangible Low-Taxed Income under the Tax Act as period costs when incurred. There was no material impact to our consolidated financial statements when our analysis was completed in the fourth quarter of 2018. 87                     10. Geographic Information The following table depicts the disaggregation of revenue by geographic region based on the ship to location of our customers and is consistent with how we evaluate our financial performance (in thousands): United States Japan Asia Pacific, excluding Japan EMEA Latin America Total Years Ended December 31, 2018 2017 2016 103,791   $ 115,536   $ 115,706 55,205   36,897   27,615   8,715   51,488   33,189   27,859   7,357   52,951 29,829 23,669 5,142 232,223   $ 235,429   $ 227,297 $ $ The  following  table  is  a  summary  of  our  long-lived  assets  which  include  property  and  equipment,  net  based  on  the  physical  location  of  the  assets  (in thousands): United States Japan Other Total 11. Employee Benefit Plan December 31, 2018 December 31, 2017 $ $ 5,525   $ 1,108   629   7,262   $ 7,733 1,510 670 9,913 We adopted a profit sharing plan qualified under Section 401(k) of the Internal Revenue Code which is offered to all of our United States employees. Participants in the plan may elect to contribute up to  $18,500  of their annual compensation to the plan for the 2018 calendar year. Individuals who are 50 or older may contribute an additional  $6,000  of their annual income. In  2018 , we matched  50%  of the first  6%  of the employee’s eligible compensation for a maximum employer contribution of $2,500 per participant. We contributed  $1.0 million , $1.0 million and $0.9 million during the years ended December 31, 2018 , 2017 and 2016 , respectively. 12. Appcito Acquisition On June 23, 2016, we entered into an asset purchase agreement with Appcito, Inc. (“Appcito”), a privately held company engaged in providing a unified set of services for applications deployed on cloud infrastructure with facilities located in Santa Clara, California and Bangalore, India. Under the terms of the purchase agreement, we acquired substantially all of the assets of Appcito. This acquisition enhances our position as a comprehensive secure application services leader. The total purchase consideration was $6.5 million . The fair value of the total purchase consideration was $6.3 million , which consisted of $5.0 million in cash consideration, less a holdback of $0.7 million , which was fully paid during the second quarter of 2017, and 227,404 unregistered shares of our common stock with an aggregated fair value of $1.3 million . 88                               The total purchase consideration was allocated to Appcito’s net tangible and intangible assets based on their estimated fair values at the acquisition date as follows (in thousands): Developed technology Goodwill Other tangible assets Total assets acquired $ $ 5,050 1,235 58 6,343 13 . Selected Quarterly Financial Data (Unaudited) Selected quarterly financial data for  2018  and  2017  is as follows (in thousands, except per share amounts): Revenue Gross profit Net loss Net loss per share - basic Net loss per share - diluted Revenue Gross profit Net income (loss) Net income (loss) per share - basic Net income (loss) per share - diluted March 31, 2018 June 30, 2018 September 30, 2018 December 31, 2018 Quarter Ended $ $ $ $ $ $ $ $ $ $ 49,183   37,299   (19,670)   (0.27)   (0.27)   March 31, 2017 63,934   49,191   (1,337)   (0.02)   (0.02)   $ $ $ $ $ $ $ $ $ $ 89 60,713   47,526   (4,532)   (0.06)   (0.06)   $ $ $ $ $ 60,502   47,488   (1,807)   (0.02)   (0.02)   Quarter Ended June 30, 2017 September 30, 2017 53,973   41,173   (7,955)   (0.11)   (0.11)   $ $ $ $ $ 62,005   48,138   (2,245)   (0.03)   (0.03)   $ $ $ $ $ $ $ $ $ $ 61,825 48,014 (1,608) (0.02) (0.02) December 31, 2017 55,517 43,609 786 0.01 0.01                                   Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure None. Item 9A. Controls and Procedures Management’s Evaluation of Disclosure Controls and Procedures Our management, with the participation of our Chief Executive Officer and Chief Financial Officer, has evaluated the effectiveness of our disclosure controls and procedures as of December 31, 2018 , as required by Rule 13a-15(b) under the Securities Exchange Act of 1934, or the Exchange Act. The term “disclosure controls and procedures,” as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act, means controls and other procedures of a company that are designed to ensure that information required to be disclosed by the company in the reports that it files or submits to the SEC, under the Exchange Act is recorded, processed, summarized and reported, within the time periods specified in the SEC’s rules and forms. Disclosure controls and procedures include, without limitation, controls and procedures designed to ensure that information required to be disclosed by a company in the reports that it files or submits under the Exchange Act is accumulated and communicated to the company’s management, including its principal executive and financial officers, as appropriate to enable timely decisions regarding required disclosure. In designing and evaluating our disclosure controls and procedures, our management recognizes that any disclosure controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving the desired control objectives. In addition, the design of disclosure controls and procedures must reflect the fact that there are resource constraints and that our management is required to apply its judgment in evaluating the benefits of possible controls and procedures relative to their costs. Based on this evaluation, our Chief Executive Officer and Chief Financial Officer, as our principal executive officer and principal financial officer, respectively, concluded that our disclosure controls and procedures were not effective as of December 31, 2018 , due to the material weaknesses in our internal controls over financial reporting described below. Notwithstanding the material weaknesses as of December 31, 2018 , management has concluded that the consolidated financial statements included in this Form 10-K present fairly, in all material respects, and in conformity with U.S. GAAP our financial position, results of operations and cash flows for the periods presented. Management’s Report on Internal Control Over Financial Reporting Our management is responsible for establishing and maintaining adequate internal control over financial reporting (as defined in Rules 13a-15(f) and 15d- 15(f) under the Exchange Act). Internal control over financial reporting consists of policies and procedures that: • • • Pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the Company; Are designed and operated to provide reasonable assurance regarding the reliability of our financial reporting and our process for the preparation of financial statements for external purposes in accordance with generally accepted accounting principles and that receipts and expenditures of the Company are being made only in accordance with authorizations of management and directors of the Company; and Provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use or disposition of the Company’s assets that could have a material effect on the financial statements. Our internal control over financial reporting is designed by, and under the supervision of our principal executive officer and principal financial officer and effected by our Board of Directors, management, and others. Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with internal control policies or procedures may deteriorate. Management has assessed the effectiveness of our internal control over financial reporting as of December 31, 2018 , using the criteria set forth in the Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring 90 Organizations of the Treadway Commission (“COSO”). A material weakness is a deficiency, or a combination of deficiencies, in internal control over financial reporting, such that there is a reasonable possibility that a material misstatement of our annual or interim financial statements will not be prevented or detected on a timely basis. In connection with management’s assessment of our internal control over financial reporting described above, management identified deficiencies that constituted individually, or in the aggregate, material weaknesses in our internal control over financial reporting as of December 31, 2018 . Material Weaknesses Identified The Company previously disclosed material weaknesses in internal control over financial reporting as of December 31, 2017 in our Annual Report on Form 10-K for the year ended December 31, 2017. The material weaknesses relate to our control environment and monitoring activities and revenue recognition. The material weaknesses led to the restatement of our annual consolidated financial statements for the years ended December 31, 2016 and 2015. As described below, management has developed and implemented remediation actions to address the material weaknesses and further actions are ongoing as of December 31, 2018. Management has reported to the Audit Committee the status of these remediation actions. Further, the Company has not had sufficient time to test the effectiveness of the remediation actions. As a result, the material weaknesses continue to be present as of December 31, 2018. These control deficiencies could have resulted in other misstatements in financial statement accounts and disclosures that would result in a material misstatement to the annual or interim consolidated financial statements that might not have been prevented or detected. Changes to Internal Control over Financial Reporting Beginning January 1, 2018, we adopted Topic 606, the new revenue recognition standard. We implemented changes to our revenue recognition policies, process and control activities to support the adoption of Topic 606. Except in relation to our adoption of Topic 606, and continued remediation actions in relation to the material weaknesses described below, no other change in our internal control over financial reporting (as defined in Rule 13a-15(f) under the Exchange Act) occurred during the quarter ended December 31, 2018 , that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting. Remediation Actions Relating to Material Weaknesses in Internal Control over Financial Reporting Management has implemented or is in the process of implementing various initiatives intended to address the identified material weaknesses and strengthen our overall internal control environment. Management has reported to the Audit Committee regarding its development and implementation of these remediation actions. In this regard, some of our key remedial initiatives include: • • • • • • Executive Management Communications to Reinforce Compliance - Our Chief Executive Officer and Chief Financial Officer, at the direction of our Board of Directors, have in communications to personnel continued to reinforce the importance of adherence to our policies and procedures regarding ethics and compliance and the importance of identifying misconduct and raising and communicating concerns. Changes to Our Executive Management and Sales Personnel - We have hired new personnel, who have enabled improved lines of communication across business functions, to address areas of identified gaps in expertise. Training Practices - We initiated development of a comprehensive training program relating to revenue recognition and contract review and have begun to deploy elements of the training to our sales personnel. Credit Policies and Procedures - We evaluated our practices regarding extension of credit to customers and evaluation of customer creditworthiness. The improved practices have been implemented and we are in the process of testing the effectiveness of those practices. Revenue Recognition Policies and Procedures - We have evaluated our revenue recognition policies and procedures and are implementing improvements. Implementation and Enhancement of Entity Level Controls - We are implementing additional controls in our quarterly/annual financial reporting process, including enhanced sub-certifications by all sales personnel, as well as other key personnel in our finance, human resources, and legal functions. The enhanced sub-certifications include specific 91 documentation related to the identification of non-standard revenue arrangements. We have also enhanced our insider trading policy and related communications to employees. Our management has worked, and continues to work, to strengthen our internal control over financial reporting. We are committed to ensuring that such controls are designed and operating effectively. The identified material weaknesses will not be considered remediated until the applicable remedial controls operate for a sufficient period of time and management concludes, through testing, that these controls are operating effectively. As we continue to evaluate and improve our internal control over financial reporting, we may take additional measures to address control deficiencies or modify or change the proposed remediation measures described above. Our Board of Directors and management take internal control over financial reporting and the integrity of our financial statements seriously and believe that the steps taken, and to be taken, to remediate the identified material weaknesses were and are essential steps to maintaining strong and effective internal control over financial reporting and a strong internal control environment. Inherent Limitations on Effectiveness of Controls Our management, including our principal executive officer and our principal financial officer, does not expect that our disclosure controls or our internal control over financial reporting will prevent or detect all error and all fraud. A control system, no matter how well-designed and operated, can provide only reasonable, not absolute, assurance that the control system’s objectives will be met. The design of a control system must reflect the fact that there are resource constraints and the benefits of controls must be considered relative to their costs. Further, because of the inherent limitations in all control systems, no evaluation of controls can provide absolute assurance that misstatements due to error or fraud will not occur or that all control issues and instances of fraud, if any, have been detected. The design of any system of controls is based in part on certain assumptions about the likelihood of future events and there can be no assurance that any design will succeed in achieving its stated goals under all potential future conditions. Projections of any evaluation of the effectiveness of controls to future periods are subject to risks. Over time, controls may become inadequate because of changes in conditions or deterioration in the degree of compliance with policies or procedures. Item 9B. Other Information None. 92 Item 10. Directors, Executive Officers and Corporate Governance PART III The information required by this item will be included in an amendment to this report or in our Proxy Statement for the 2019 Annual Meeting of Stockholders and is incorporated by reference in this report. Item 11. Executive Compensation The information required by this item will be included in an amendment to this report or in our Proxy Statement for the 2019 Annual Meeting of Stockholders and is incorporated by reference in this report. Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters The information required by this item will be included in an amendment to this report or in our Proxy Statement for the 2019 Annual Meeting of Stockholders and is incorporated by reference in this report. Item 13. Certain Relationships and Related Transactions, and Director Independence. The information required by this item will be included in an amendment to this report or in our Proxy Statement for the 2019 Annual Meeting of Stockholders and is incorporated by reference in this report. Item 14. Principal Accounting Fees and Services The information required by this item will be included in an amendment to this report or in our Proxy Statement for the 2019 Annual Meeting of Stockholders and is incorporated by reference in this report. 93 PART IV Item 15. Exhibits, Financial Statement Schedules (a) We have filed the following documents are filed as part of this Annual Report on Form 10-K: 1. Consolidated Financial Statements Our Consolidated Financial Statements are listed in the Index to Consolidated Financial Statements in Part II, Item 8 of this Annual Report on Form 10-K. 2. Consolidated Financial Statement Schedules All other schedules have been omitted as they are not required, not applicable, or the required information is otherwise included. 3. Exhibits. The following exhibits are filed with or incorporated by reference in this report, in each case as indicated therein (numbered in accordance with Item 601 of Regulation S-K). EXHIBIT INDEX Incorporated by Reference Exhibit Number Description Form   SEC File No. Exhibit Number   Amended and Restated Certificate of Incorporation of the Registrant   8-K    001-36343   Amended and Restated Bylaws of the Registrant   Amendment to Bylaws of the Registrant   Amended and Restated Bylaws of the Registrant   Form of common stock certificate of the Registrant Amended and Restated Investors’ Rights Agreement among the Registrant and certain holders of its capital stock, amended as of October 4, 2013 Form of Indemnification Agreement between the Registrant and each of its directors and executive officers   S-1/A   333-194015   8-K   8-K    001-36343    001-36343   S-1/A   333-194015 S-1/A 333-194015   3.1   3.2   3.2   3.2   4.1 4.2 Filed Herewith Filing Date   November 9. 2018       March 10, 2014   November 9. 2018       January 8, 2019   March 10, 2014 March 10, 2014 S-1/A 333-194015 10.1 March 10, 2014   2008 Stock Plan and forms of agreements thereunder   Amended and Restated 2014 Equity Incentive Plan   Amended 2014 Employee Stock Purchase Plan   10-Q   10-Q   001-36343   001-36343   2014 Employee Stock Purchase Plan and forms of agreements thereunder   S-1/A   333-194015   Form of Stock Option Agreement pursuant to the 2008 Stock Plan   10-Q   001-36343 Form of Stock Option Agreement- Early Exercise pursuant to the 2008 Stock Plan 10-Q 001-36343 Form of Stock Option Agreement pursuant to the Amended and Restated 2014 Equity Incentive Plan 10-Q 001-36343 Form of Restricted Stock Unit Agreement pursuant to the Amended and Restated 2014 Equity Incentive Plan 10-Q 001-36343   Offer Letter, dated July 30, 2004, by and between the Registrant and Lee Chen   S-1/A   333-194015 Offer Letter, dated November 3, 2008, by and between the Registrant and Rajkumar Jalan S-1/A 333-194015   10.2   10.1   10.5   10.2 10.3 10.4 10.5   10.6 10.7   May 13, 2014   August 6, 2015   March 10, 2014   August 4, 2014 August 4, 2014 August 4, 2014 August 4, 2014   March 10, 2014 March 10, 2014 Offer Letter, dated January 4, 2012, by and between the Registrant and Robert Cochran S-1/A 333-194015 10.9 March 10, 2014 X 94 3.1 3.2 3.3 3.4 4.1 4.2 10.1* 10.2* 10.3* 10.4* 10.5* 10.6* 10.7* 10.8* 10.9* 10.10* 10.11* 10.12*                                                                                                                                                                   Exhibit Number 10.13 10.14 10.15 10.16 10.17 10.18 10.19 10.20 10.21 10.22 10.23 10.24 10.25 10.26 10.27* 10.28* 10.29 10.30 10.31* 10.32* 10.33* 10.34* 10.35* 21.1 23.1 31.1 Description Reseller Agreement, dated April 2, 2009, by and between the Registrant and NEC Corporation First Amendment to Reseller Agreement, dated May 19, 2011, by and between the Registrant and NEC Corporation Second Amendment to Reseller Agreement, dated April 1, 2011, by and between the Registrant and NEC Corporation Third Amendment to Reseller Agreement, dated April 1, 2011, by and between the Registrant and NEC Corporation Fourth Amendment to Reseller Agreement, dated October 3, 2011, by and between the Registrant and NEC Corporation Fifth Amendment to Reseller Agreement, dated April 2, 2012, by and between the Registrant and NEC Corporation Sixth Amendment to Reseller Agreement, dated November 29, 2012, by and between the Registrant and NEC Corporation Seventh Amendment to Reseller Agreement, dated April 9, 2013, by and between the Registrant and NEC Corporation Eighth Amendment to Reseller Agreement, dated October 22, 2013, by and between the Registrant and NEC Corporation Ninth Amendment to Reseller Agreement, executed on April 22, 2014, by and between the Registrant and NEC Corporation Manufacturing Services Agreement, dated December 8, 2006, by and between the Registrant and Lanner Electronics (USA) Amendment No. 1 to Manufacturing Services Agreement, dated June 27, 2013, by and between the Registrant and Lanner Electronics (USA) Contract Manufacturer Agreement, dated July 1, 2008, by and between the Registrant and AEWIN Technologies, Inc. Amendment No. 1 to Contract Manufacturer Agreement, dated June 30, 2014, by and between the Registrant and AEWIN Technologies, Inc.   Form of Change in Control and Severance Agreement   Executive Incentive Compensation Plan First Amendment to Loan and Security Agreement, dated as of September 5, 2018, between A10 Networks, Inc. and Silicon Valley Bank Loan and Security Agreement, dated as of November 1, 2016, between A10 Networks, Inc. and Silicon Valley Bank Transition Letter, dated March 29, 2017, by and between the Registrant and Greg Straughn Offer Letter, dated May 14, 2017, by and between the Registrant and Tom Constantino Transition Agreement, dated November 6, 2017, by and between the Registrant and Rey Smets Offer Letter, dated December 15, 2017, by and between the Registrant and Christopher White Letter Agreement, dated as of March 14, 2018, among A10 Networks, Inc., VIEX Opportunities Fund, LP - Series One, VIEX GP, LLC, VIEX Special Opportunities Fund II, LP, VIEX Special Opportunities GP II, LLC, VIEX Capital Advisors, LLC and Eric Singer.   List of subsidiaries of the Registrant Consent of Deloitte & Touche LLP, independent registered public accounting firm Certification of Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act 95 Incorporated by Reference Form   S-1/A SEC File No. Exhibit Number Filing Date Filed Herewith 333-194015 10.12 February 18, 2014 S-1/A 333-194015 10.13 February 18, 2014 S-1/A 333-194015 10.14 February 18, 2014 S-1/A 333-194015 10.15 February 18, 2014 S-1/A 333-194015 10.16 February 18, 2014 S-1/A 333-194015 10.17 February 18, 2014 S-1/A 333-194015 10.18 February 18, 2014 S-1/A 333-194015 10.19 February 18, 2014 S-1/A 333-194015 10.20 February 18, 2014 10-Q 001-36343 10.1 August 4, 2014 S-1/A 333-194015 10.21 February 18, 2014 S-1/A 333-194015 10.22 February 18, 2014 S-1/A 333-194015 10.23 February 18, 2014 10-K 001-36343 10.31 March 11, 2015   S-1/A   333-194015   10-K   001-6343 10-Q 001-36343   10.25   10.32 10.2   March 10, 2014   March 1, 2016 September 24, 2018 10-Q 001-36343 10-Q 001-36343 10-Q 001-36343 10.1 10.1 10.1 November 3, 2016 May 5, 2017 August 3, 2017 10-K 001-36343 10.32 August 29, 2018 10-K 001-36343 10.33 August 29, 2018 8-K 001-36343 10.1 March 16, 2018 X X X                                                                                                                                                                                                                                                                                                                                                                                       Exhibit Number 31.2 32.1 ** 32.2 ** 101.INS 101.SCH 101.CAL 101.DEF Description Certification of Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act Certification of Chief Executive Officer pursuant to Section 906 of the Sarbanes-Oxley Act Certification of Chief Financial Officer pursuant to Section 906 of the Sarbanes-Oxley Act   XBRL Instance Document.   XBRL Taxonomy Extension Schema Document.   XBRL Taxonomy Extension Calculation Linkbase Document.   XBRL Taxonomy Extension Definition Linkbase Document. 101.LAB   XBRL Taxonomy Extension Label Linkbase Document. 101.PRE   XBRL Taxonomy Extension Presentation Linkbase Document. Incorporated by Reference Form   SEC File No. Exhibit Number Filing Date Filed Herewith X X X X X X X X X * ** Indicates a management contract or compensatory plan. The certifications attached as Exhibit 32.1 and 32.2 that accompany this Annual Report on Form 10‑K are not deemed filed with the Securities and Exchange Commission and are not to be incorporated by reference into any filing of A10 Networks, Inc. under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, whether made before or after the date of this Annual Report on Form 10‑K, irrespective of any general incorporation language contained in such filing. Item 16. Form 10-K Summary None. 96                                                                                                                                                                                         Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized. SIGNATURES A10 NETWORKS, INC. Date: March 15, 2019 By: /s/ Lee Chen Lee Chen Chief Executive Officer and President (Principal Executive Officer) Pursuant to the requirements of the Securities Exchange Act of 1934, this annual report on Form 10-K has been signed below by the following persons on behalf of the Registrant and in the capacities and on the date indicated. Signature /s/ Lee Chen Lee Chen /s/ Tom Constantino Tom Constantino /s/ Peter Y. Chung Peter Y. Chung /s/ Alan S. Henricks Alan S. Henricks /s/ Phillip J. Salsbury Phillip J. Salsbury /s/ Tor R. Braham Tor R. Braham Title Date Chief Executive Officer, President and Chairman of the Board March 15, 2019 (Principal Executive Officer) Chief Financial Officer March 15, 2019 (Principal Financial and Accounting Officer) Director Director Director Director 97 March 15, 2019 March 15, 2019 March 15, 2019 March 15, 2019                                                                                                                                                                         A10 NETWORKS, INC. 2014 EMPLOYEE STOCK PURCHASE PLAN (As amended October 22, 2018) Exhibit 10.4 1. Purpose . The purpose of the Plan is to provide employees of the Company and its Designated Companies with an opportunity to purchase Common Stock through accumulated Contributions. The Company intends for the Plan to have two components: a Code Section 423 Component (“423 Component”) and a non-Code Section 423 Component (“Non-423 Component”). The Company’s intention is to have the 423 Component of the Plan qualify as an “employee stock purchase plan” under Section 423 of the Code. The provisions of the 423 Component, accordingly, will be construed so as to extend and limit Plan participation in a uniform and nondiscriminatory basis consistent with the requirements of Section 423 of the Code. In addition, this Plan authorizes the grant of an option to purchase shares of Common Stock under the Non-423 Component that does not qualify as an “employee stock purchase plan” under Section 423 of the Code; such an option will be granted pursuant to rules, procedures, or sub-plans adopted by the Administrator designed to achieve tax, securities laws, or other objectives for Eligible Employees and the Company. Except as otherwise provided herein, the Non-423 Component will operate and be administered in the same manner as the 423 Component. 2.      Definitions . (a)      “ Administrator ” means the Board or any Committee designated by the Board to administer the Plan pursuant to Section 14. interest. (b)           “ Affiliate ” means any entity, other than a Subsidiary, in which the Company has an equity or other ownership (c)      “ Amendment Date ” means October 22, 2018. (d)      “ Applicable Laws ” means the requirements relating to the administration of equity-based awards under U.S. state corporate laws, U.S. federal and state securities laws, the Code, any stock exchange or quotation system on which the Common Stock is listed or quoted and the applicable laws of any foreign country or jurisdiction where options are, or will be, granted under the Plan. (e)      “ Board ” means the Board of Directors of the Company. (f)      “ Change in Control ” means the occurrence of any of the following events: (i)      A change in the ownership of the Company which occurs on the date that any one person, or more than one person acting as a group (“ Person ”), acquires ownership of the stock of the Company that, together with the stock held by such Person, constitutes more than fifty percent (50%) of the total voting power of the stock of the Company; provided, however, that for purposes of this subsection, the acquisition of additional stock by any one Person, who is considered to own more than fifty percent (50%) of the total voting power of the stock of the Company will not be considered a Change in Control; or (ii)      A change in the effective control of the Company which occurs on the date that a majority of members of the Board is replaced during any twelve (12) month period by Directors whose appointment or election is not endorsed by a majority of the members of the Board prior to the date of the appointment or election. For purposes of this clause (ii), if any Person is considered to be in effective control of the Company, the acquisition of additional control of the Company by the same Person will not be considered a Change in Control; or (iii)      A change in the ownership of a substantial portion of the Company’s assets which occurs on the date that any Person acquires (or has acquired during the twelve (12) month period ending on the date of the most recent acquisition by such person or persons) assets from the Company that have a total gross fair market value equal to or more than fifty percent (50%) of the total gross fair market value of all of the assets of the Company immediately prior to such acquisition or acquisitions; provided, however, that for purposes of this subsection, the following will not constitute a change in the ownership of a substantial portion of the Company’s assets: (A) a transfer to an entity that is controlled by the Company’s stockholders immediately after the transfer, or (B) a transfer of assets by the Company to: (1) a stockholder of the Company (immediately before the asset transfer) in exchange for or with respect to the Company’s stock, (2) an entity, fifty percent (50%) or more of the total value or voting power of which is owned, directly or indirectly, by the Company, (3) a Person, that owns, directly or indirectly, fifty percent (50%) or more of the total value or voting power of all the outstanding stock of the Company, or (4) an entity, at least fifty percent (50%) of the total value or voting power of which is owned, directly or indirectly, by a Person described in this subsection (iii)(B)(3). For purposes of this subsection, gross fair market value means the value of the assets of the Company, or the value of the assets being disposed of, determined without regard to any liabilities associated with such assets. For purposes of this definition, persons will be considered to be acting as a group if they are owners of a corporation that enters into a merger, consolidation, purchase or acquisition of stock, or similar business transaction with the Company. Notwithstanding the foregoing, a transaction will not be deemed a Change in Control unless the transaction qualifies as a change in control event within the meaning of Code Section 409A, as it has been and may be amended from time to time, and any proposed or final U.S. Treasury Regulations and Internal Revenue Service guidance that has been promulgated or may be promulgated thereunder from time to time. Further and for the avoidance of doubt, a transaction will not constitute a Change in Control if: (i) its sole purpose is to change the state of the Company’s incorporation, or (ii) its sole purpose is to create a holding company that will be owned in substantially the same proportions by the persons who held the Company’s securities immediately before such transaction. (g)      “ Code ” means the U.S. Internal Revenue Code of 1986, as amended. Reference to a specific section of the Code or U.S. Treasury Regulation thereunder will include such section or regulation, any valid regulation or other official applicable guidance promulgated under such section, and any comparable provision of any future legislation or regulation amending, supplementing or superseding such section or regulation. (h)      “ Committee ” means a committee of the Board appointed in accordance with Section 14 hereof. (i)      “ Common Stock ” means the common stock of the Company. 2 (j)      “ Company ” means A10 Networks, Inc., a Delaware corporation, or any successor thereto. (k)           “ Compensation ” means an Eligible Employee’s base straight time gross earnings, but exclusive of payments for incentive compensation, bonuses, payments for overtime and shift premium, equity compensation income and other similar compensation. The Administrator, in its discretion, may, on a uniform and nondiscriminatory basis, establish a different definition of Compensation for a subsequent Offering Period. (l)      “ Contributions ” means the payroll deductions and other additional payments that the Company may permit to be made by a Participant to fund the exercise of options granted pursuant to the Plan. (m)      “ Designated Company ” means any Subsidiary or Affiliate that has been designated by the Administrator from time to time in its sole discretion as eligible to participate in the Plan. For purposes of the 423 Component, only the Company and its Subsidiaries may be Designated Companies, provided, however that at any given time, a Subsidiary that is a Designated Company under the 423 Component will not be a Designated Company under the Non-423 Component. (n)      “ Director ” means a member of the Board. (o)      “ Eligible Employee ” means any individual who is a common law employee providing services to the Company or a Designated Company and is customarily employed for at least twenty (20) hours per week and more than five (5) months in any calendar year by the Employer, or any lesser number of hours per week and/or number of months in any calendar year established by the Administrator (if required under applicable local law) for purposes of any separate Offering or for Eligible Employees participating in the Non-423 Component. For purposes of the Plan, the employment relationship will be treated as continuing intact while the individual is on sick leave or other leave of absence that the Employer approves or is legally protected under Applicable Laws. Where the period of leave exceeds three (3) months and the individual’s right to reemployment is not guaranteed either by statute or by contract, the employment relationship will be deemed to have terminated three (3) months and one (1) day following the commencement of such leave. The Administrator, in its discretion, from time to time may, prior to an Enrollment Date for all options to be granted on such Enrollment Date in an Offering, determine (on a uniform and nondiscriminatory basis or as otherwise permitted by Treasury Regulation Section 1.423‑2) that the definition of Eligible Employee will or will not include an individual if he or she: (i) has not completed at least two (2) years of service since his or her last hire date (or such lesser period of time as may be determined by the Administrator in its discretion), (ii) customarily works not more than twenty (20) hours per week (or such lesser period of time as may be determined by the Administrator in its discretion), (iii) customarily works not more than five (5) months per calendar year (or such lesser period of time as may be determined by the Administrator in its discretion), (iv) is a highly compensated employee within the meaning of Section 414(q) of the Code, or (v) is a highly compensated employee within the meaning of Section 414(q) of the Code with compensation above a certain level or is an officer or subject to the disclosure requirements of Section 16(a) of the Exchange Act, provided the exclusion is applied with respect to each Offering in an identical manner to all highly compensated individuals of the Employer whose Employees are participating in that Offering. Each exclusion will be applied with respect to an Offering in a manner complying with U.S. Treasury Regulation Section 1.423‑2(e)(2)(ii). 3 (p)      “ Employer ” means the employer of the applicable Eligible Employee(s). (q)      “ Enrollment Date ” means the first Trading Day of each Offering Period. (r)      “ Exchange Act ” means the U.S. Securities Exchange Act of 1934, as amended, including the rules and regulations promulgated thereunder. (s)      “ Exercise Date ” means the last Trading Day of the Purchase Period. Notwithstanding the foregoing, in the event that an Offering Period is terminated prior to its expiration pursuant to Section 20(a), the Administrator, in its sole discretion, may determine that any Purchase Period also terminating under such Offering Period will terminate without options being exercised on the Exercise Date that otherwise would have occurred on the last Trading Day of such Purchase Period. (t)      “ Fair Market Value ” means, as of any date and unless the Administrator determines otherwise, the value of Common Stock determined as follows: (i)      If the Common Stock is listed on any established stock exchange or a national market system, including without limitation the New York Stock Exchange, NASDAQ Global Select Market, the NASDAQ Global Market or the NASDAQ Capital Market of The NASDAQ Stock Market, its Fair Market Value will be the closing sales price for such stock (or the closing bid, if no sales were reported) as quoted on such exchange or system on the date of determination, as reported in The Wall Street Journal or such other source as the Administrator deems reliable; (ii)           If the Common Stock is regularly quoted by a recognized securities dealer but selling prices are not reported, its Fair Market Value will be the mean between the high bid and low asked prices for the Common Stock on the date of determination (or if no bids and asks were reported on that date, as applicable, on the last Trading Day such bids and asks were reported), as reported in The Wall Street Journal or such other source as the Administrator deems reliable; (iii)      In the absence of an established market for the Common Stock, the Fair Market Value thereof will be determined in good faith by the Administrator; or (u)      “ Fiscal Year ” means the fiscal year of the Company. (v)      “ New Exercise Date ” means a new Exercise Date if the Administrator shortens any Offering Period then in progress. (w)      “ Offering ” means an offer under the Plan of an option that may be exercised during an Offering Period as further described in Section 4. For purposes of the Plan, the Administrator may designate separate Offerings under the Plan (the terms of which need not be identical) in which Employees of one or more Employers will participate, even if the dates of the applicable Offering Periods of each such Offering are identical and the provisions of the Plan will separately apply to each Offering. To the extent permitted by U.S. Treasury Regulation Section 1.423‑2(a)(1), the terms of each Offering need not be identical provided that the terms of the Plan and an Offering together satisfy U.S. Treasury Regulation Section 1.423‑2(a)(2) and (a)(3). (x)      “ Offering Periods ” means the periods of approximately six (6) months during which an option granted pursuant to the Plan may be exercised, (i) commencing on the first Trading Day on or after December 1 and June 1 of each year and terminating on the last Trading Day on or before June 1 and December 1, respectively, approximately six (6) months later; provided, however, that the first Offering Period under the Plan occurring on or after the Amendment Date will commence with the first Trading Day on or after 4 December 3, 2018, and will end on the last Trading Day on or before May 31, 2019. The duration and timing of Offering Periods may be changed pursuant to Sections 4, 20 and 30. (y)      “ Parent ” means a “parent corporation,” whether now or hereafter existing, as defined in Section 424(e) of the Code. (z)      “ Participant ” means an Eligible Employee that participates in the Plan. (aa)      “ Plan ” means this A10 Networks, Inc. 2014 Employee Stock Purchase Plan, as amended from time to time. (bb)      “ Purchase Period ” means the period during an Offering Period and during which shares of Common Stock may be purchased on a Participant’s behalf in accordance with the terms of the Plan. Unless the Administrator provides otherwise, Purchase Periods will have the same duration as, and coincide with the timing of, the Offering Period to which it relates. (cc)           “ Purchase Price ” means an amount equal to eighty-five percent (85%) of the Fair Market Value of a share of Common Stock on the Enrollment Date or on the Exercise Date, whichever is lower; provided however, that the Purchase Price may be determined for subsequent Offering Periods by the Administrator subject to compliance with Section 423 of the Code (or any successor rule or provision or any other Applicable Law, regulation or stock exchange rule) or pursuant to Section 20. (dd)      “ Registration Date ” means the effective date of the first registration statement that is filed by the Company and declared effective pursuant to Section 12(g) of the Exchange Act, with respect to any class of the Company’s securities. (ee)      “ Subsidiary ” means a “subsidiary corporation,” whether now or hereafter existing, as defined in Section 424(f) of the Code. trading. (ff)      “ Trading Day ” means a day on which the national stock exchange upon which the Common Stock is listed is open for (gg)           “ U.S. Treasury Regulations ” means the Treasury regulations of the Code. Reference to a specific Treasury Regulation or Section of the Code will include such Treasury Regulation or Section, any valid regulation promulgated under such Section, and any comparable provision of any future legislation or regulation amending, supplementing or superseding such Section or regulation. 3.      Eligibility . (a)      Offering Periods . Any Eligible Employee on a given Enrollment Date will be eligible to participate in the Plan, subject to the requirements of Section 5. (b)      Non-U.S. Employees . Eligible Employees who are citizens or residents of a non-U.S. jurisdiction (without regard to whether they also are citizens or residents of the United States or resident aliens (within the meaning of Section 7701(b)(1)(A) of the Code)) may be excluded from participation in the Plan or an Offering if the participation of such Eligible Employees is prohibited under the laws of the applicable jurisdiction or if complying with the laws of the applicable jurisdiction would cause the Plan or an Offering to violate Section 423 of the Code. In the case of the Non-423 Component, Eligible Employees may be excluded from participation in the Plan or an Offering if the Administrator has determined that participation of such Eligible Employees is not advisable or practicable. 5 (c)           Limitations . Any provisions of the Plan to the contrary notwithstanding, no Eligible Employee will be granted an option under the Plan (i) to the extent that, immediately after the grant, such Eligible Employee (or any other person whose stock would be attributed to such Eligible Employee pursuant to Section 424(d) of the Code) would own capital stock of the Company or any Parent or Subsidiary of the Company and/or hold outstanding options to purchase such stock possessing five percent (5%) or more of the total combined voting power or value of all classes of the capital stock of the Company or of any Parent or Subsidiary of the Company, or (ii) to the extent that his or her rights to purchase stock under all employee stock purchase plans (as defined in Section 423 of the Code) of the Company or any Parent or Subsidiary of the Company accrues at a rate, which exceeds twenty-five thousand dollars ($25,000) worth of stock (determined at the Fair Market Value of the stock at the time such option is granted) for each calendar year in which such option is outstanding at any time, as determined in accordance with Section 423 of the Code and the regulations thereunder. 4.      Offering Periods . The Plan will be implemented by consecutive Offering Periods with a new Offering Period commencing on the first Trading Day on or after December 1 and June 1 each year, or on such other date as the Administrator will determine; provided, however, that the first Offering Period under the Plan on or after the Amendment Date will commence with the first Trading Day on or after the December 3, 2018 and end on the last Trading Day on or before May 31, 2019. The Administrator will have the power to change the duration of Offering Periods (including the commencement dates thereof) with respect to future Offerings without stockholder approval if such change is announced prior to the scheduled beginning of the first Offering Period to be affected thereafter; provided, however, that no Offering Period may last more than twenty-seven (27) months. 5.      Participation . An Eligible Employee may participate in the Plan pursuant to Section 3(a) by (i) submitting to the Company’s stock administration office (or its designee), on or before a date determined by the Administrator prior to an applicable Enrollment Date, a properly completed subscription agreement authorizing Contributions in the form provided by the Administrator for such purpose, or (ii) following an electronic or other enrollment procedure determined by the Administrator. 6.      Contributions . (a)      At the time a Participant enrolls in the Plan pursuant to Section 5, he or she will elect to have Contributions (in the form of payroll deductions or otherwise, to the extent permitted by the Administrator) made on each pay day during the Offering Period in an amount not exceeding ten percent (10%) of the Compensation, which he or she receives on each pay day during the Offering Period. The Administrator, in its sole discretion, may permit all Participants in a specified Offering to contribute amounts to the Plan through payment by cash, check or other means set forth in the subscription agreement prior to each Exercise Date of each Purchase Period. A Participant’s subscription agreement will remain in effect for successive Offering Periods unless terminated as provided in Section 10 hereof. (b)      In the event Contributions are made in the form of payroll deductions, such payroll deductions for a Participant will commence on the first pay day following the Enrollment Date and will end on the last pay day on or prior to the last Exercise Date of such Offering Period to which such authorization is applicable, unless sooner terminated by the Participant as provided in Section 10 hereof. 6 (c)      All Contributions made for a Participant will be credited to his or her account under the Plan and Contributions will be made in whole percentages only. A Participant may not make any additional payments into such account (unless required by Applicable Laws). (d)           A Participant may discontinue his or her participation in the Plan as provided under Section 10. Unless otherwise determined by the Administrator, during a Purchase Period, a Participant may not increase the rate of his or her Contributions and may only decrease the rate of his or her Contributions one (1) time and such decrease must be to a Contribution rate of zero percent (0%). Any such decrease during a Purchase Period requires the Participant (i) properly completing and submitting to the Company’s stock administration office (or its designee), on or before a date determined by the Administrator prior to an applicable Exercise Date, a new subscription agreement authorizing the change in Contribution rate in the form provided by the Administrator for such purpose, or (ii) following an electronic or other procedure prescribed by the Administrator. If a Participant has not followed such procedures to change the rate of Contributions, the rate of his or her Contributions will continue at the originally elected rate throughout the Purchase Period and future Offering Periods and Purchase Periods (unless the Participant’s participation is terminated as provided in Sections 10 or 11). The Administrator may, in its sole discretion, amend the nature and/or number of Contribution rate changes that may be made by Participants during any Offering Period or Purchase Period and may establish other conditions or limitations as it deems appropriate for Plan administration. Any change in payroll deduction rate made pursuant to this Section 6(d) will be effective as of the first (1 st ) full payroll period following five (5) business days after the date on which the change is made by the Participant (unless the Administrator, in its sole discretion, elects to process a given change in payroll deduction rate more quickly). (e)           Notwithstanding the foregoing, to the extent necessary to comply with Section 423(b)(8) of the Code and Section 3(d), a Participant’s Contributions may be decreased to zero percent (0%) at any time during a Purchase Period. Subject to Section 423(b)(8) of the Code and Section 3(d) hereof, Contributions will recommence at the rate originally elected by the Participant effective as of the beginning of the first Purchase Period scheduled to end in the following calendar year, unless terminated by the Participant as provided in Section 10. (f)           Notwithstanding any provisions to the contrary in the Plan, the Administrator may allow Eligible Employees to participate in the Plan via cash contributions instead of payroll deductions if (i) payroll deductions are not permitted under applicable local law, (ii) the Administrator determines that cash contributions are permissible under Section 423 of the Code; or (iii) for Participants participating in the Non-423 Component. (g)      At the time the option is exercised, in whole or in part, or at the time some or all of the Common Stock issued under the Plan is disposed of (or any other time that a taxable event related to the Plan occurs), the Participant must make adequate provision for the Company’s or Employer’s federal, state, local or any other tax liability payable to any authority including taxes imposed by jurisdictions outside of the U.S., national insurance, social security or other tax withholding obligations, if any, which arise upon the exercise of the option or the disposition of the Common Stock (or any other time that a taxable event related to the Plan occurs). At any time, the Company or the Employer may, but will not be obligated to, withhold from the Participant’s compensation the amount necessary for the Company or the Employer to meet applicable withholding obligations, including any withholding required to make available to the Company or the Employer any tax deductions or benefits attributable to sale or early disposition of Common Stock by the Eligible Employee. In addition, the Company or the Employer may, but will not be obligated to, withhold from the proceeds of the 7 sale of Common Stock or any other method of withholding the Company or the Employer deems appropriate to the extent permitted by U.S. Treasury Regulation Section 1.423‑2(f). 7.      Grant of Option . On the Enrollment Date of each Offering Period, each Eligible Employee participating in such Offering Period will be granted an option to purchase on each Exercise Date during such Offering Period (at the applicable Purchase Price) up to a number of shares of Common Stock determined by dividing such Eligible Employee’s Contributions accumulated prior to such Exercise Date and retained in the Eligible Employee’s account as of the Exercise Date by the applicable Purchase Price; provided that in no event will an Eligible Employee be permitted to purchase during each Purchase Period more than 1,500 shares of Common Stock (subject to any adjustment pursuant to Section 19) and provided further that such purchase will be subject to the limitations set forth in Sections 3(c) and 13. The Eligible Employee may accept the grant of such option under the Plan by electing to participate in the Plan in accordance with the requirements of Section 5. The Administrator may, for future Offering Periods, increase or decrease, in its absolute discretion, the maximum number of shares of Common Stock that an Eligible Employee may purchase during each Purchase Period or Offering Period. Exercise of the option will occur as provided in Section 8, unless the Participant has withdrawn pursuant to Section 10. The option will expire on the last day of the Offering Period. 8.      Exercise of Option . (a)      Unless a Participant withdraws from the Plan as provided in Section 10, his or her option for the purchase of shares of Common Stock will be exercised automatically on the Exercise Date, and the maximum number of full shares subject to the option will be purchased for such Participant at the applicable Purchase Price with the accumulated Contributions from his or her account. No fractional shares of Common Stock will be purchased; any Contributions accumulated in a Participant’s account, which are not sufficient to purchase a full share will be retained in the Participant’s account for the subsequent Purchase Period or Offering Period, subject to earlier withdrawal by the Participant as provided in Section 10. Any other funds left over in a Participant’s account after the Exercise Date will be returned to the Participant. During a Participant’s lifetime, a Participant’s option to purchase shares hereunder is exercisable only by him or her. (b)      If the Administrator determines that, on a given Exercise Date, the number of shares of Common Stock with respect to which options are to be exercised may exceed (i) the number of shares of Common Stock that were available for sale under the Plan on the Enrollment Date of the applicable Offering Period, or (ii) the number of shares of Common Stock available for sale under the Plan on such Exercise Date, the Administrator may in its sole discretion (x) provide that the Company will make a pro rata allocation of the shares of Common Stock available for purchase on such Enrollment Date or Exercise Date, as applicable, in as uniform a manner as will be practicable and as it will determine in its sole discretion to be equitable among all Participants exercising options to purchase Common Stock on such Exercise Date, and continue all Offering Periods then in effect or (y) provide that the Company will make a pro rata allocation of the shares available for purchase on such Enrollment Date or Exercise Date, as applicable, in as uniform a manner as will be practicable and as it will determine in its sole discretion to be equitable among all participants exercising options to purchase Common Stock on such Exercise Date, and terminate any or all Offering Periods then in effect pursuant to Section 20. The Company may make a pro rata allocation of the shares available on the Enrollment Date of any applicable Offering Period pursuant to the preceding sentence, notwithstanding any authorization of additional shares for issuance under the Plan by the Company’s stockholders subsequent to such Enrollment Date. 8 9.      Delivery . As soon as reasonably practicable after each Exercise Date on which a purchase of shares of Common Stock occurs, the Company will arrange the delivery to each Participant of the shares purchased upon exercise of his or her option in a form determined by the Administrator (in its sole discretion) and pursuant to rules established by the Administrator. The Company may permit or require that shares be deposited directly with a broker designated by the Company or to a designated agent of the Company, and the Company may utilize electronic or automated methods of share transfer. The Company may require that shares be retained with such broker or agent for a designated period of time and/or may establish other procedures to permit tracking of disqualifying dispositions of such shares. No Participant will have any voting, dividend, or other stockholder rights with respect to shares of Common Stock subject to any option granted under the Plan until such shares have been purchased and delivered to the Participant as provided in this Section 9. 10.      Withdrawal . (a)      A Participant may withdraw all but not less than all the Contributions credited to his or her account and not yet used to exercise his or her option under the Plan at any time by (i) submitting to the Company’s stock administration office (or its designee) a written notice of withdrawal in the form determined by the Administrator for such purpose (which may be similar to the form attached hereto as Exhibit B), or (ii) following an electronic or other withdrawal procedure determined by the Administrator. All of the Participant’s Contributions credited to his or her account will be paid to such Participant promptly after receipt of notice of withdrawal and such Participant’s option for the Offering Period will be automatically terminated, and no further Contributions for the purchase of shares will be made for such Offering Period. If a Participant withdraws from an Offering Period, Contributions will not resume at the beginning of the succeeding Offering Period, unless the Participant re-enrolls in the Plan in accordance with the provisions of Section 5. (b)      A Participant’s withdrawal from an Offering Period will not have any effect upon his or her eligibility to participate in any similar plan that may hereafter be adopted by the Company or in succeeding Offering Periods that commence after the termination of the Offering Period from which the Participant withdraws. 11.      Termination of Employment . Unless otherwise required by Applicable Laws, upon a Participant’s ceasing to be an Eligible Employee, for any reason, he or she will be deemed to have elected to withdraw from the Plan and the Contributions credited to such Participant’s account during the Offering Period but not yet used to purchase shares of Common Stock under the Plan will be returned to such Participant or, in the case of his or her death, to the person or persons entitled thereto under Section 15, and such Participant’s option will be automatically terminated. A Participant whose employment transfers between entities through a termination with an immediate rehire (with no break in service) by the Company or a Designated Company will not be treated as terminated under the Plan; however, if a Participant transfers from an Offering under the 423 Component to the Non-423 Component, the exercise of the option will be qualified under the 423 Component only to the extent it complies with Section 423 of the Code. 12.      Interest . No interest will accrue on the Contributions of a participant in the Plan, except as may be required by Applicable Law, as determined by the Company, and if so required by the laws of a particular jurisdiction, will apply to all Participants in the relevant Offering under the 423 Component, except to the extent otherwise permitted by U.S. Treasury Regulation Section 1.423‑2(f). 9 13.      Stock . (a)      Subject to adjustment upon changes in capitalization of the Company as provided in Section 19 hereof, the maximum number of shares of Common Stock that will be made available for sale under the Plan will be 6,857,971 shares of Common Stock. (b)      Until the shares of Common Stock are issued (as evidenced by the appropriate entry on the books of the Company or of a duly authorized transfer agent of the Company), a Participant will have only the rights of an unsecured creditor with respect to such shares, and no right to vote or receive dividends or any other rights as a stockholder will exist with respect to such shares. (c)           Shares of Common Stock to be delivered to a Participant under the Plan will be registered in the name of the Participant or in the name of the Participant and his or her spouse. 14.      Administration . The Plan will be administered by the Board or a Committee appointed by the Board, which Committee will be constituted to comply with Applicable Laws. The Administrator will have full and exclusive discretionary authority to construe, interpret and apply the terms of the Plan, to designate separate Offerings under the Plan, to designate Subsidiaries and Affiliates as participating in the 423 Component or Non-423 Component, to determine eligibility, to adjudicate all disputed claims filed under the Plan and to establish such procedures that it deems necessary for the administration of the Plan (including, without limitation, to adopt such procedures and sub-plans as are necessary or appropriate to permit the participation in the Plan by employees who are foreign nationals or employed outside the U.S., the terms of which sub-plans may take precedence over other provisions of this Plan, with the exception of Section 13(a) hereof, but unless otherwise superseded by the terms of such sub-plan, the provisions of this Plan will govern the operation of such sub- plan). Unless otherwise determined by the Administrator, the Employees eligible to participate in each sub-plan will participate in a separate Offering or in the Non-423 Component. Without limiting the generality of the foregoing, the Administrator is specifically authorized to adopt rules and procedures regarding eligibility to participate, the definition of Compensation, handling of Contributions, making of Contributions to the Plan (including, without limitation, in forms other than payroll deductions), establishment of bank or trust accounts to hold Contributions, payment of interest, conversion of local currency, obligations to pay payroll tax, determination of beneficiary designation requirements, withholding procedures and handling of stock certificates that vary with applicable local requirements. The Administrator also is authorized to determine that, to the extent permitted by U.S. Treasury Regulation Section 1.423‑2(f), the terms of an option granted under the Plan or an Offering to citizens or residents of a non-U.S. jurisdiction will be less favorable than the terms of options granted under the Plan or the same Offering to employees resident solely in the U.S. Every finding, decision and determination made by the Administrator will, to the full extent permitted by law, be final and binding upon all parties. 15.      Designation of Beneficiary . (a)      If permitted by the Administrator, a Participant may file a designation of a beneficiary who is to receive any shares of Common Stock and cash, if any, from the Participant’s account under the Plan in the event of such Participant’s death subsequent to an Exercise Date on which the option is exercised but prior to delivery to such Participant of such shares and cash. In addition, if permitted by the Administrator, a Participant may file a designation of a beneficiary who is to receive any cash from the Participant’s account under the Plan in the event of such Participant’s death prior to exercise of the option. If a Participant is married and the designated beneficiary is not the spouse, spousal consent will be required for such designation to be effective. 10 (b)      Such designation of beneficiary may be changed by the Participant at any time by notice in a form determined by the Administrator. In the event of the death of a Participant and in the absence of a beneficiary validly designated under the Plan who is living at the time of such Participant’s death, the Company will deliver such shares and/or cash to the executor or administrator of the estate of the Participant, or if no such executor or administrator has been appointed (to the knowledge of the Company), the Company, in its discretion, may deliver such shares and/or cash to the spouse or to any one or more dependents or relatives of the Participant, or if no spouse, dependent or relative is known to the Company, then to such other person as the Company may designate. (c)      All beneficiary designations will be in such form and manner as the Administrator may designate from time to time. Notwithstanding Sections 15(a) and (b) above, the Company and/or the Administrator may decide not to permit such designations by Participants in non-U.S. jurisdictions to the extent permitted by U.S. Treasury Regulation Section 1.423‑2(f). 16.      Transferability . Neither Contributions credited to a Participant’s account nor any rights with regard to the exercise of an option or to receive shares of Common Stock under the Plan may be assigned, transferred, pledged or otherwise disposed of in any way (other than by will, the laws of descent and distribution or as provided in Section 15 hereof) by the Participant. Any such attempt at assignment, transfer, pledge or other disposition will be without effect, except that the Company may treat such act as an election to withdraw funds from an Offering Period in accordance with Section 10 hereof. 17.      Use of Funds . The Company may use all Contributions received or held by it under the Plan for any corporate purpose, and the Company will not be obligated to segregate such Contributions except under Offerings or for Participants in the Non-423 Component for which Applicable Laws require that Contributions to the Plan by Participants be segregated from the Company’s general corporate funds and/or deposited with an independent third party. Until shares of Common Stock are issued, Participants will have only the rights of an unsecured creditor with respect to such shares. 18.           Reports . Individual accounts will be maintained for each Participant in the Plan. Statements of account will be given to participating Eligible Employees at least annually, which statements will set forth the amounts of Contributions, the Purchase Price, the number of shares of Common Stock purchased and the remaining cash balance, if any. 19.      Adjustments, Dissolution, Liquidation, Merger or Change in Control . (a)      Adjustments . In the event that any dividend or other distribution (whether in the form of cash, Common Stock, other securities, or other property), recapitalization, stock split, reverse stock split, reorganization, merger, consolidation, split-up, spin-off, combination, repurchase, or exchange of Common Stock or other securities of the Company, or other change in the corporate structure of the Company affecting the Common Stock occurs, the Administrator, in order to prevent dilution or enlargement of the benefits or potential benefits intended to be made available under the Plan, will, in such manner as it may deem equitable, adjust the number and class of Common Stock that may be delivered under the Plan, the Purchase Price per share and the number of shares of Common Stock covered by each option under the Plan that has not yet been exercised, and the numerical limits of Sections 7 and 13. 11 (b)           Dissolution or Liquidation . In the event of the proposed dissolution or liquidation of the Company, any Offering Period then in progress will be shortened by setting a New Exercise Date, and will terminate immediately prior to the consummation of such proposed dissolution or liquidation, unless provided otherwise by the Administrator. The New Exercise Date will be before the date of the Company’s proposed dissolution or liquidation. The Administrator will notify each Participant in writing or electronically, prior to the New Exercise Date, that the Exercise Date for the Participant’s option has been changed to the New Exercise Date and that the Participant’s option will be exercised automatically on the New Exercise Date, unless prior to such date the Participant has withdrawn from the Offering Period as provided in Section 10 hereof. (c)      Merger or Change in Control . In the event of a merger or Change in Control, each outstanding option will be assumed or an equivalent option substituted by the successor corporation or a Parent or Subsidiary of the successor corporation. In the event that the successor corporation refuses to assume or substitute for the option, the Offering Period with respect to which such option relates will be shortened by setting a New Exercise Date on which such Offering Period will end. The New Exercise Date will occur before the date of the Company’s proposed merger or Change in Control. The Administrator will notify each Participant in writing or electronically prior to the New Exercise Date, that the Exercise Date for the Participant’s option has been changed to the New Exercise Date and that the Participant’s option will be exercised automatically on the New Exercise Date, unless prior to such date the Participant has withdrawn from the Offering Period as provided in Section 10 hereof. 20.      Amendment or Termination . (a)      The Administrator, in its sole discretion, may amend, suspend, or terminate the Plan, or any part thereof, at any time and for any reason. If the Plan is terminated, the Administrator, in its discretion, may elect to terminate all outstanding Offering Periods either immediately or upon completion of the purchase of shares of Common Stock on the next Exercise Date (which may be sooner than originally scheduled, if determined by the Administrator in its discretion), or may elect to permit Offering Periods to expire in accordance with their terms (and subject to any adjustment pursuant to Section 19). If the Offering Periods are terminated prior to expiration, all amounts then credited to Participants’ accounts that have not been used to purchase shares of Common Stock will be returned to the Participants (without interest thereon, except as otherwise required under Applicable Laws, as further set forth in Section 12 hereof) as soon as administratively practicable. (b)           Without stockholder consent and without limiting Section 20(a), the Administrator will be entitled to change the Offering Periods or Purchase Periods, designate separate Offerings, limit the frequency and/or number of changes in the amount withheld during an Offering Period, establish the exchange ratio applicable to amounts withheld in a currency other than U.S. dollars, permit Contributions in excess of the amount designated by a Participant in order to adjust for delays or mistakes in the Company’s processing of properly completed Contribution elections, establish reasonable waiting and adjustment periods and/or accounting and crediting procedures to ensure that amounts applied toward the purchase of Common Stock for each Participant properly correspond with Contribution amounts, and establish such other limitations or procedures as the Administrator determines in its sole discretion advisable that are consistent with the Plan. 12 (c)      In the event the Administrator determines that the ongoing operation of the Plan may result in unfavorable financial accounting consequences, the Administrator may, in its discretion and, to the extent necessary or desirable, modify, amend or terminate the Plan to reduce or eliminate such accounting consequence including, but not limited to: (i)      amending the Plan to conform with the safe harbor definition under the Financial Accounting Standards Board Accounting Standards Codification Topic 718 (or any successor thereto), including with respect to an Offering Period underway at the time; Purchase Period underway at the time of the change in Purchase Price; (ii)           altering the Purchase Price for any Offering Period or Purchase Period including an Offering Period or Period or Purchase Period underway at the time of the Administrator action; (iii)      shortening any Offering Period or Purchase Period by setting a New Exercise Date, including an Offering (iv)      reducing the maximum percentage of Compensation a Participant may elect to set aside as Contributions; and Purchase Period. (v)           reducing the maximum number of Shares a Participant may purchase during any Offering Period or Such modifications or amendments will not require stockholder approval or the consent of any Participants. 21.      Notices . All notices or other communications by a Participant to the Company under or in connection with the Plan will be deemed to have been duly given when received in the form and manner specified by the Company at the location, or by the person, designated by the Company for the receipt thereof. 22.      Conditions Upon Issuance of Shares . Shares of Common Stock will not be issued with respect to an option unless the exercise of such option and the issuance and delivery of such shares pursuant thereto will comply with all applicable provisions of law, domestic or foreign, including, without limitation, the U.S. Securities Act of 1933, as amended, the Exchange Act, the rules and regulations promulgated thereunder, and the requirements of any stock exchange upon which the shares may then be listed, and will be further subject to the approval of counsel for the Company with respect to such compliance. As a condition to the exercise of an option, the Company may require the person exercising such option to represent and warrant at the time of any such exercise that the shares are being purchased only for investment and without any present intention to sell or distribute such shares if, in the opinion of counsel for the Company, such a representation is required by any of the aforementioned applicable provisions of law. 23.      Code Section 409A. The 423 Component of the Plan is intended to be exempt from the application of Code Section 409A, and to the extent not exempt, is intended to comply with Code Section 409A, and any ambiguities or ambiguous terms herein will be interpreted to so be exempt from or comply with Code Section 409A. In furtherance of the foregoing and notwithstanding any provision in the Plan to the contrary, if the Administrator determines that an option granted under the Plan may be subject to Code Section 409A or that any provision in the Plan would cause an option under the Plan to be subject to Code Section 409A, the Administrator may amend the terms of the Plan and/or of an outstanding option granted under the Plan, or take such other action the Administrator determines is necessary or appropriate, in each case, without the Participant’s consent, to exempt any outstanding option or future option that may be granted under the Plan from or to allow any such options to comply with Code Section 409A, but only to the extent any such amendments 13 or action by the Administrator would not violate Code Section 409A. Notwithstanding the foregoing, in no event will the Company or any Parent, Subsidiary or Affiliate have any liability or obligation to reimburse, indemnify, or hold harmless a Participant or any other party if the option to purchase Common Stock under the Plan that is intended to be exempt from or compliant with Code Section 409A is not so exempt or compliant or for any action taken by the Administrator with respect thereto. The Company makes no representation that the option to purchase Common Stock under the Plan is exempt from or compliant with Code Section 409A. 24.      Term of Plan . The Plan will become effective upon the later to occur of (a) its adoption by the Board or (b) the business day immediately prior to the Registration Date. It will continue in effect for a term of twenty (20) years, unless sooner terminated under Section 20. 25.      Stockholder Approval . The Plan will be subject to approval by the stockholders of the Company within twelve (12) months after the date the Plan is adopted by the Board. Such stockholder approval will be obtained in the manner and to the degree required under Applicable Laws. 26.      Governing Law . The Plan will be governed by, and construed in accordance with, the laws of the State of California (except its choice-of-law provisions). 27.      No Right to Employment . Participation in the Plan by a Participant will not be construed as giving a Participant the right to be retained as an employee of the Company or a Subsidiary or Affiliate, as applicable. Further, the Company or a Subsidiary or Affiliate may dismiss a Participant from employment at any time, free from any liability or any claim under the Plan. 28.      Severability . If any provision of the Plan is or becomes or is deemed to be invalid, illegal, or unenforceable for any reason in any jurisdiction or as to any Participant, such invalidity, illegality or unenforceability will not affect the remaining parts of the Plan, and the Plan will be construed and enforced as to such jurisdiction or Participant as if the invalid, illegal or unenforceable provision had not been included. 29. Compliance with Applicable Laws . The terms of this Plan are intended to comply with all Applicable Laws and will be construed accordingly. 14 SUBSIDIARIES OF THE REGISTRANT Exhibit 21.1 Subsidiary Name A10 Networks, Anguilla, Ltd. A10 Networks (Australia) Pty Ltd. A10 Networks Inc. (Beijing) A10 Networks, Inc. - Taiwan A10 Networks India Private Limited A10 Networks Israel Ltd. A10 Networks, KK A10 Networks Limited A10 Networks Singapore Pte. Ltd. Shanghai A10 Networks Technology Co., Ltd. A10 Networks Malaysia Sdn. Bhd. Jurisdiction of Incorporation or Organization Anguilla Australia China Taiwan, Republic of China India Israel Japan United Kingdom Singapore China Malaysia         CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM We consent to the incorporation by reference in Registration Statement Nos. 333-194719, 333-202652, 333-209835, 333-212954, 333-216208 and 333- 227781  on  Form  S-8  of  our  report  dated  March  15,  2019  ,  relating  to  the  consolidated  financial  statements  of  A10  Networks,  Inc.  and  its  subsidiaries  (the “Company”) (which report expresses an unqualified opinion and includes an explanatory paragraph relating to the Company’s adoption of Accounting Standards Update No. 2014-09 Revenue from Contracts with Customers (Topic 606)) appearing in the Annual Report on Form 10-K of A10 Networks, Inc. for the year ended December 31, 2018. Exhibit 23.1 /S/ DELOITTE & TOUCHE LLP San Jose, California March 15, 2019 Exhibit 31.1 I, Lee Chen, certify that: CERTIFICATION 1. 2. 3. 4. I have reviewed this Annual Report on Form 10-K of A10 Networks, Inc. for the quarter ended December 31, 2018 ; Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report; Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report; The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have: (a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared; (b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles; (c) (d) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and 5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions): (a) (b) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.  Date: March 15, 2019 By: /s/ Lee Chen Lee Chen President and Chief Executive Officer       Exhibit 31.2 I, Tom Constantino , certify that: CERTIFICATION 1. 2. 3. 4. I have reviewed this Annual Report on Form 10-K of A10 Networks, Inc. for the quarter ended December 31, 2018 ; Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report; Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report; The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f) for the registrant and have: (a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared; (b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles; (c) (d) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and 5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions): (a) (b) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting. Date: March 15, 2019 By: /s/ Tom Constantino Tom Constantino Executive Vice President and Chief Financial Officer (Principal Accounting and Financial Officer)         Exhibit 32.1 CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002 In connection with the Annual Report on Form 10-K of A10 Networks, Inc. (the “Company”) for the period ended December 31, 2018 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Lee Chen, President and Chief Executive Officer of the Company, certify pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that: (1) (2) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company. Date: March 15, 2019 By: /s/ Lee Chen Lee Chen President and Chief Executive Officer         Exhibit 32.2 CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002 In connection with the Annual Report on Form 10-K of A10 Networks, Inc. (the “Company”) for the period ended December 31, 2018 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Tom Constantino , Executive Vice President and Chief Financial Officer of the Company, certify pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that: (1) (2) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company. Date: March 15, 2019 By: /s/ Tom Constantino Tom Constantino Executive Vice President and Chief Financial Officer (Principal Accounting and Financial Officer)         

Continue reading text version or see original annual report in PDF format above