Mattermost (https://mattermost.com) is an open-core collaboration and workflow automation platform for air-gapped, on-prem and private clouds. Our customers are in defense, intelligence, security and critical infrastructure, including the USAF and NASA. Y Combinator led our Series B, their largest open-source investment at the time.
Both openings are full stack on the core platform: Go backend, React/TypeScript frontend, PostgreSQL and Redis. The codebase is public (https://github.com/mattermost/mattermost), so most of what you build is too. We would rather hire people who ship and own complex software end to end than chase an exact stack match, so any systems or backend language and any frontend stack counts. What we look for in both roles: REST and WebSocket APIs with real networking fundamentals (HTTP, connection lifecycle), and relational databases including schema design and query optimization.
We use coding agents daily (Claude Code, Cursor, and others) at every stage of the work: planning, building, reviewing, testing, and shipping. We treat that as core craft rather than a shortcut around the fundamentals. If you have a track record of shipping and owning complex software end-to-end, we want to hear from you.
Senior Full Stack Engineer $142,723 - $172,723 USD Architect and ship full stack features end to end, own the testing strategy for what you ship, and build internal tooling and testing infrastructure that makes the rest of the team faster. You will work without close supervision and hold the security and compliance bar our customers require. Nice to have: distributed systems and high availability architecture, regulated-environment security, open-source contributions, experience on remote-first teams.
Join our team: https://job-boards.greenhouse.io/mattermost/jobs/5379251008
Staff Full Stack Engineer $172,724 - $227,135 USD Set technical direction for the platform rather than for a feature area: architecture and roadmap across the stack, the standards for how the org uses coding agents, and the strategy for internal tooling and testing. You will influence direction across teams, partner with security and compliance on it, and mentor senior engineers. Nice to have: staff, principal or tech lead experience elsewhere, open-source maintainership, FedRAMP or ITAR familiarity, defense or critical infrastructure background.
Join our team: https://job-boards.greenhouse.io/mattermost/jobs/5405811008
Both roles have Canadian postings: https://job-boards.greenhouse.io/mattermost

Multiple roles at Mattermost