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Mattermost is a collaborative workflow platform trusted by the U.S. Department of War, Fortune 500s, and critical infrastructure operators. The platform delivers secure messaging, file sharing, workflow automation, audio/screenshare, and project management with full data and operational control, running on-premises and in private clouds.
We are seeking a Senior Full Stack Engineer to 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 meet strict security, compliance, and reliability requirements.
Key responsibilities include architecting and building full-stack features optimized for scalability and performance across Go, React, TypeScript, PostgreSQL, and Redis. You will 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. You'll develop internal tooling and testing infrastructure to speed up team delivery, own testing strategy across frontend and backend code, design and consume REST and WebSocket APIs, maintain security and compliance standards required by government and enterprise clients, and contribute to Mattermost's open-source codebase.
Required qualifications include strong full-stack development experience in Go and React or 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 with judgment to know when to trust output and when to take control, and a bias toward shipping and owning complex software end-to-end without close supervision.
Nice-to-have qualifications include 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 on distributed or remote-first teams, and experience building tools, skills, or workflows on top of AI coding agents.
Success is measured by shipping full-stack features using an AI-forward agentic development workflow in the first 90 days, building internal tooling and testing infrastructure that measurably speeds up team delivery by month 6, and being recognized as the team's driver of agentic engineering practice by year one while deepening ownership of distributed systems and contributing actively to the open-source codebase.
Mattermost offers mission-driven work supporting organizations that depend on secure collaboration, a remote-first culture with a globally distributed high-trust team, an AI-forward environment where agentic development is core craft, end-to-end ownership of complex software across the full stack, and participation in a vibrant open-source developer community.
