Senior Fullstack TypeScript Engineer – Stabilize Auth

We have a TypeScript monorepo SaaS platform with 5 frontend apps, a Fastify backend API, and PostgreSQL — all deployed to Google Cloud Run behind Firebase Hosting.

After a recent feature (role-based access control with app-scoped permissions), our staging and production environments are broken. The issues span authentication flows, cookie handling across multiple apps, middleware redirect logic, database migrations, and deployment configuration — all intertwined.

We've been stuck for over a week with various commits and things are not stabilizing.

We already have a DevOps engineer handling CI/CD and infrastructure. What we need is a fullstack engineer who can own the

application-level stabilization: diagnose root causes, fix the auth/cookie/RBAC code, and get staging working end-to-end.

### What's broken (symptoms)

• Backend fails to start on Cloud Run (startup probe timeout)
• Auth flow doesn't complete in staging/production (works locally)
• Cookiebased sessions not working across the multiapp Firebase Hosting setup
• RBAC enforcement causing redirect loops or blocking legitimate users
• Database migrations may not have run on staging
• Root cause analysis is part of the job — we're unsure where code bugs end and config issues begin

### Tech stack

• TypeScript (strict), 15 (App Router, Server Actions, middleware), React 1
• Fastify 5 backend with plugin architecture
• Firebase Authentication + custom RS256 JWT system (jose library)
• Cookiebased sessions (httpOnly authtoken + appcontext cookies)
• PostgreSQL with Drizzle ORM
• Google Cloud Run (6 services), Firebase Hosting (routing/proxy)
• pnpm workspaces + Turborepo monorepo
• GitHub Actions CI/CD

### Scope

1.

Diagnose — Review recent changes, map the auth flow end-to-end, identify root causes

2.

Fix backend — Get the Fastify backend starting and healthy on Cloud Run

3.

Fix auth flow — Login → JWT cookie → authenticated requests across all 5 apps

4.

Fix RBAC — App-scoped permissions working correctly with fail-closed security

5.

Verify staging — Full end-to-end verification on staging environment

### What we're looking for

• Deep experience with

middleware, cookies, and auth flows — this is the core problem

• Has worked with cookies across subdomains and Firebase Hosting rewrites
• Experience with

Firebase Auth + custom JWT systems

• Comfortable with

Fastify and backend debugging

• Strong

diagnostic skills — finding root causes matters as much as writing fixes

• Can work independently and communicate findings clearly

### Engagement model

Fixed-price, milestone-based. If shortlisted, we'll share a detailed technical brief with the full codebase architecture so you can provide an informed estimate.

### How to apply

• Describe your experience with

authentication systems, cookie-based sessions, or multi-app deployments

• Share a brief example of a

similar debugging/stabilization project you've completed

• Your

availability to start — we need someone who can begin immediately.

• Any

questions about the scope?

### Skills:

`TypeScript` `` `React` `` `Fastify` `Firebase Authentication` `JWT` `RBAC` `Google Cloud Run` `PostgreSQL` `Cookie Handling` `Auth Middleware` `Monorepo`

Contract duration of 1 to 3 months.

Mandatory skills:

Firebase, TypeScript, React,