Senior Full Stack Engineer - Mattermost

About Mattermost

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 delivers secure messaging, file sharing, workflow automation, and project management with full data and operational control.

The Role

We are seeking a Senior Full Stack Engineer to help build and scale our core web platform. You will contribute across our Go backend and React/TypeScript web frontend, building features that meet strict security, compliance, and reliability requirements. Our engineering culture is AI-forward; we expect engineers to work fluently with AI coding agents (e.g., Claude Code, Cursor) as a core part of their daily craft.

What You Will Do

• Architect and build full-stack features optimized for scalability using Go, React, TypeScript, PostgreSQL, and Redis.
• Leverage AI coding agents for scaffolding, refactoring, and testing while maintaining full accountability for security and design.
• Develop internal tooling and testing infrastructure to accelerate team delivery.
• Own the testing strategy across your frontend and backend code.
• Design and consume REST and WebSocket APIs with solid networking fundamentals.
• Maintain security and compliance standards required by government and enterprise clients.
• Contribute to Mattermost's open-source codebase.

What We Are Looking For

• Required: Strong full-stack experience in Go and React (or comparable stacks).
• Required: Experience with REST/WebSocket APIs and relational databases (PostgreSQL).
• Required: Hands-on daily fluency with AI coding agents (Claude Code, Cursor, Copilot).
• Required: A bias toward shipping and owning complex software end-to-end.
• Nice to Have: Experience with distributed systems, high-availability architecture, or regulated-environment security.
• Nice to Have: Background in defense/intelligence sectors or open-source contributions.

Why Mattermost

• Mission-Driven: Support critical missions for the U.S. Department of War and global infrastructure.
• Remote-First: Work from anywhere with a high-trust, autonomous team.
• AI-Forward: Agentic development is core to our engineering culture.
• Ownership: Real accountability for the software you build.

U.S. Eligibility & Compliance

This role may require obtaining and maintaining a U.S. government security clearance. Applicants must meet eligibility requirements for access to export-controlled information (EAR/ITAR). Mattermost is an EEO employer.