Senior NestJS Backend Engineer, Part-Time PR Reviewer (Prisma, PostgreSQL, Firebase Auth)

About us K9 Genius builds a dog-training mobile app and a web learning platform for dog trainers, both running on a NestJS API. The web frontend (Next.js) is starting to integrate with the API, beginning with signup and login. We need senior oversight on backend changes, especially anything touching authentication, the database or security. The role Part-time, ongoing. You will review and approve backend pull requests and give the team focused technical guidance. A project manager owns tickets and priorities, and a QA engineer owns testing, so this is a technical review role only. What you'll do - Review and approve backend PRs for correctness, security, reliability and maintainability - Check schema changes, migrations, authentication flows and authorisation boundaries carefully - Help scope the API work for the Next.js signup/login integration without duplicating existing endpoints - Flag missing tests, possible credential exposure and unsafe changes before they're merged or deployed - Mentor our backend developer and escalate higher-risk architecture decisions to the PM What good looks like - Assigned PRs are reviewed within the agreed turnaround time - Every review ends in a clear outcome: approve, or request changes with specific comments the developer can act on - Schema migrations and auth/permission changes are never merged without your review - Missing tests and security risks are flagged in the PR before merge, not found after deployment You need - Strong production experience with Node.js, TypeScript and NestJS REST APIs - Strong PostgreSQL and Prisma, including safe schema migrations and data integrity - Firebase Authentication, bearer-token validation, permissions and secure backend design - Ability to review API contracts, validation, error handling, tests, sensitive data flows and deployment risk - Comfortable with GitHub PR workflows and giving clear, constructive feedback in written English Nice to have - NestJS testing (e.g. Vitest), Docker, GitHub Actions, Google Cloud Run - Experience as a senior reviewer or tech lead on a live SaaS or consumer app How to apply 1. Answer the screening questions. 2. Include a short Loom video (2-3 minutes) introducing yourself and walking through a backend project or a code review you're proud of. Shortlisted candidates will do a short sample review of a sanitised NestJS PR, focusing on authorisation, migration safety and testing. No live secrets or production access are shared during screening.