Staff Software Engineer - Security Platform: Authentication

An overview of this role

As a Staff Software Engineer on GitLab's Authentication team, you'll be the technical lead for how every user, application, token, and automated agent proves who it is on GitLab.com, Self-Managed, and Dedicated.

We're an OAuth 2.0 and OpenID Connect (OIDC) provider for millions of users. We also accept identity from enterprise identity providers through Security Assertion Markup Language (SAML) and Lightweight Directory Access Protocol (LDAP). Behind that sit more than ten token types and several session methods that grew inside the Ruby on Rails monolith. You'll help us move this work onto GATE, GitLab's new authentication and authorization platform. GATE exchanges external credentials for short-lived tokens at the edge through a Secure Token Service written in Go.You'll set our technical direction, lead the hardest protocol and migration work yourself, and help senior engineers own the rest.

Our projects include:

• OAuth across Cells: Making OAuth clients, grants, and tokens work when users and organizations live in different cells
• Global identities: One user identity that works across organizations and cells
• Token consolidation: Reducing the number of token types and moving token issuance and validation out of the monolith
• Identity for artificial intelligence (AI) agents and workloads: OAuth for Model Context Protocol (MCP) clients, workload identity federation, and service identities with narrow scopes

What you'll do

• Own the technical direction for authentication protocols at GitLab, including OAuth 2.0, OIDC, SAML, and token exchange, across the Rails monolith and GATE services.
• Write and drive design documents and architecture decision records (ADRs) for multi-quarter work, then break that work into increments that ship behind feature flags.
• Lead migrations that must not break existing customers: token formats, client and grant state, and session behavior on GitLab.com, Self-Managed, and Dedicated.
• Be hands-on in the most complex parts of the code, in Ruby on Rails and Go, and review the designs and merge requests of other engineers.
• Agree interface contracts with the GATE Core, GATE Infra, Authorization, and Tenant Scale (Cells and Organizations) teams, and keep them current as the architecture changes.
• Treat authentication as a security and availability boundary: threat-model new flows, add rate limits and abuse controls, and lead the technical response to authentication incidents.
• Mentor senior and intermediate engineers on the team and raise the protocol and security knowledge of the whole group.
• Work asynchronously with engineers in India, Europe, and the Americas, with most decisions made in writing.
• Take part in on-call or operational support where your team’s ownership model requires it.

What you'll bring

• Significant experience building and running production authentication or identity systems at scale, with technical leadership across teams that moves unclear problems to written decisions and shipped code.
• Deep, hands-on knowledge of OAuth 2.0 and OIDC: authorization code with Proof Key for Code Exchange (PKCE), refresh token rotation, token exchange, client registration, scopes, and JSON Web Tokens (JWTs) with signing keys and key rotation.
• Working knowledge of SAML 2.0 single sign-on and enterprise identity integration (LDAP, System for Cross-domain Identity Management (SCIM), or similar).
• Strong production experience in Ruby on Rails or Go, willingness to work in both, and experience with careful refactors, feature-flagged rollouts, and backward-compatible migrations in large, long-lived codebases.
• A security mindset. You think about token theft, replay, revocation, and blast radius before you think about elegance.
• Experience with multi-tenant software as a service (SaaS) systems, including data isolation and performance under high request volume.
• Clear, concise written English and comfort working in an all-remote, asynchronous company.
• Optional experience: authentication libraries (Doorkeeper, Devise, or OmniAuth), passkeys or multi-factor authentication, workload identity, gateways or policy engines, AI agent authentication, or multi-region architectures. Contributions to identity standards or open source identity projects are also welcome.

About the team

The Authentication group is part of the Security Platform stage, alongside Authorization, GATE Core, GATE Infra, Secrets Manager, and other security teams. We own sign-in, single sign-on, OAuth, and personal and service tokens. Our work touches every GitLab customer, and much of it is on the critical path for Cells and for GitLab's AI agent platform.