Build GATE, GitLab's new identity/access-management plane, while migrating auth off the Rails monolith

GitLab's Authentication team is building GATE, a centralized service for token issuance, validation, and identity that will underpin GitLab.com SaaS, Self-Managed, Dedicated, and air-gapped deployments. This Senior Backend Engineer role spans Ruby (Rails monolith) and Go (GATE), covering SSO/SAML/OIDC/SCIM/LDAP, passkeys, service accounts, and composite identities for AI agents.

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What this interview tests

Authentication/identity system design (OAuth, OIDC, SAML, SCIM, LDAP, JWT, RBAC)
Token issuance, validation, cryptographic signing, and key management
Migrating functionality out of a Rails monolith into a new service (GATE) across multiple deployment models
Ruby and Go proficiency in a mission-critical SaaS context
Security vulnerability triage (HackerOne-style reports) and access-management hardening
Driving technical direction/roadmap and code-review standards as a senior IC

Common question themes

Design a token issuance and validation service that must work identically across multi-tenant SaaS, self-managed, and air-gapped deployments

How would you migrate an authentication code path out of a Rails monolith into a new Go service without breaking existing customers

Explain how you'd implement or evaluate passwordless/passkey authentication

Walk through triaging and remediating a reported authentication vulnerability

Describe a time you worked across two very different codebases/languages on the same feature

How do you decide what belongs in shared internal engineering standards vs. team-specific judgment calls

How candidates describe it

Real Senior Software Engineer (RoR/Go) interview stories — retold from candidates' public write-ups, with sources.

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Interviewed June 2020 · Bangalore, IN

Google · L4 Software EngineerNo offer

Google L4 Software Engineer Interview: Eight Rounds, No Offer

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Interviewed February 2024 · Not specified

Google · L5 Software EngineerNo offer

Google L5 software engineer interview: phone screening, three onsite rounds, system design, and a late rejection

A candidate interviewing for an L5 role went through a phone screening, three onsite coding rounds, a mobile system design round, and a Googleyness and Leadership round. Two of the four technical rounds went poorly by the candidate's own assessment, and after roughly two months of silence the recruiter reported that the role had been closed.

Interviewed January 2023 · Not specified

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