Senior React Native Engineer

Mattermost is the leading collaborative workflow platform for defense, intelligence, security, and critical infrastructure. Trusted by the U.S. Department of War and Fortune 500s, our platform runs on-premises and in private clouds, delivering secure messaging, file sharing, workflow automation, audio/screenshare, and project management—all with full data and operational control. Mattermost powers high-stakes workflows across mission planning, real-time, real-world operations, DevSecOps, incident response, and cyber defense—enabling secure collaboration from tactical edge and DDIL environments to enterprise HQ. Teams operate across web, desktop, and mobile, with embedded interoperability for Microsoft Teams, Outlook, and Microsoft 365. To learn more, visit www.mattermost.com Mattermost is seeking a Senior React Native Engineer to join our mobile engineering team and build resilient mobile experiences for mission-critical industries like defense, intelligence, and critical infrastructure. This is not a feature development role: you'll be focused on the networking, architecture, and reliability challenges of running a real-time collaboration platform in DDIL environments where connectivity is unreliable and message delivery is non-negotiable. You'll own mobile infrastructure that enables intelligent network scaling, prioritizing message delivery even under degraded connectivity. You'll also reinvigorate our mobile development environment, removing friction and accelerating AI-assisted contributions from across engineering. Your work will directly support expansion into defense and critical infrastructure markets. This role offers the unique opportunity to contribute to our open-source platform while solving hard networking, state, and architecture problems that serve some of the world's most important missions. Responsibilities Include Architect DDIL-resilient networking layers for our React Native app on iOS and Android Collaborate with backend engineers on WebSocket reliability, API integration, and data sync under intermittent connectivity Design and maintain offline-first storage, intelligent network scaling, and sync/conflict resolution Stabilize the mobile dev environment and improve codebase structure, test coverage, and tooling to unblock engineers and AI-assisted development across the org Optimize app performance: networking efficiency, bundle size, startup time, memory usage Implement testing strategies and debug mobile-specific issues across platforms, devices, and OS versions, with emphasis on network failure scenarios Code reviews and mentorship on mobile architecture and networking best practices Contribute to Mattermost's open-source React Native codebase Ensure our mobile app meets security and compliance requirements for enterprise and government clients Requirements BS in Computer Science, Computer Engineering, or related field/experience 5+ years developing mobile applications, with 3+ years in React Native Strong proficiency in JavaScript/TypeScript and React ecosystem including hooks, state management (Redux, Zustand, or similar), and component architecture Deep understanding of mobile networking: HTTP, WebSockets, connection lifecycle management, retry strategies, and behavior under degraded network conditions Experience designing offline-first architectures, local data persistence, and sync/conflict resolution Experience with native iOS and Android development and the ability to write native modules when needed Proficiency with reactive programming patterns (RxJS) and local database solutions (WatermelonDB) Proficiency with AI/LLM tools to improve and accelerate development Solid understanding of mobile app deployment for both App Store and Google Play Store Familiarity with mobile testing frameworks and debugging tools for React Native Understanding of mobile security best practices and secure coding principles Strong problem-solving skills and ability to work independently in a remote, distributed team Excellent written and verbal communication skills for collaborating across time zones For candidates residing in the U.S.: This role may require the ability to obtain and maintain a U.S. government security clearance in the future. As such, U.S. applicants must be U.S. citizens and eligible under applicable clearance requirements. Applicants must meet eligibility requirements for access to export-controlled information as defined by U.S. export control laws, including EAR and ITAR. Preferences Previous experience building end user products for enterprises or secu