Senior Full Stack 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 We are seeking a Senior Full Stack Engineer to help build and scale Mattermost's core web platform for teams operating in defense and critical infrastructure sectors. You will contribute across our Go backend and React/TypeScript web frontend, building features that hold up under strict security, compliance, and reliability requirements. Our engineering culture is AI-forward. We expect engineers to work fluently with AI coding agents such as Claude Code day-to-day — for scaffolding, refactors, code review, and test generation — and treat that as core craft rather than a shortcut. We would rather hire smart people who get stuff done than chase an exact tech-stack match. If you have a track record of shipping and owning complex software end-to-end, we want to hear from you. What You Will Do Architect and build full-stack features optimized for scalability and performance across Go, React, TypeScript, PostgreSQL, and Redis Leverage AI coding agents such as Claude Code and Cursor as a core part of your daily workflow while retaining full accountability for correctness, security, and design decisions Develop internal tooling and testing infrastructure to speed up the team's delivery, including agentic workflows and skills that make AI tooling more effective for the broader team Own testing strategy across frontend and backend code you ship Design and consume REST and WebSocket APIs with solid networking fundamentals Maintain the security and compliance standards required by our government and enterprise clients Contribute to Mattermost's open-source codebase What We Are Looking For Required: Strong full-stack development experience in Go and React, or a comparable stack Experience designing and consuming REST and WebSocket APIs with solid networking fundamentals Relational database experience including PostgreSQL, schema design, and query optimization Hands-on daily fluency directing AI coding agents such as Claude Code, Cursor, or Copilot for scaffolding, refactors, code review, and test generation — with the judgment to know when to trust the output and when to take the wheel yourself Bias toward shipping and owning complex software end-to-end without close supervision Nice to Have: Experience with distributed systems or high-availability service architecture Familiarity with enterprise or regulated-environment security requirements Background in defense, intelligence, or critical infrastructure products Open-source contributions Experience working on distributed or remote-first teams Experience building tools, skills, or workflows on top of AI coding agents including MCP servers, agent skills, or CI-integrated agents How Success Is Measured First 90 Days: Shipping full-stack features on the core platform using an AI-forward agentic development workflow and owning testing strategy across the code you ship. By Month 6: Internal tooling and testing infrastructure built that measurably speeds up the broader team's delivery. Agentic development practices adopted and contributing to team-wide velocity. At Year One: Recognized as the team's driver of agentic engineering practice. Deepening ownership of distributed systems and high-availability architecture. Contri…