Node.JS Developer

We are partnering with a US-based health-tech company on the takeover of a production AI-powered mobile coaching platform. You will join the Polish team responsible for the platform's Backend-for-Frontend (BFF) and supporting Node services as they transition from the original engineering team to ours.

As Senior Node Engineer you will be the Deputy Tech Lead for the BFF/Node track.

This is a player-coach role: ~70% hands‑on engineering, ~30% leadership.

• Read and document the existing BFF codebase alongside the outgoing engineering team
• Produce a quality baseline: test coverage, Type Script strictness, lint compliance, dependency freshness, CI duration, flake rate
• Lead the knowledge‑transfer sessions for the BFF service from the client's team
• Identify the highest‑risk subsystems and propose stabilisation plans
• Set the squad's code‑review standards, branching model, and definition of done

• Own architecture decisions for the BFF service
• Lead design reviews for new endpoints, especially the AI integration surface
• Pair with mid-level engineers and review their work
• Represent the BFF squad in cross‑team architecture discussions
• Participate in on‑call rotation once we take production ownership

Must-have skills

• 5+ years Node.js in production, 3+ years NestJS
• Strong Type Script — strict mode, generics, type narrowing, no any‑as‑escape‑hatch
• NestJS depth: modules, providers, DI scope, guards, interceptors, pipes, custom decorators
• REST API design at scale; familiarity with BFF / API‑gateway patterns
• Graph
  
  QL or schema federation comfort (not required to be primary stack)
• Mongo
  
  DB in production — Mongoose or native driver, schema design, indexing
• Auth0 integration — both user authentication flows and Machine‑to‑Machine (M2M) client credentials
• AWS production experience — ECS or EKS, IAM, VPC, RDS, Elasti Cache
• CI/CD on Git Hub Actions
• Distributed tracing and structured logging in production environments
• Comfortable writing tests (Jest) and raising coverage on legacy code
• Code-review and mentorship experience

Nice-to-haves

• Datadog APM, log correlation, custom metrics
• Web Socket / WSS (the AI chat surface uses streaming)
• OpenAPI/Swagger contract‑first workflows
• Prior gateway / aggregator / BFF role
• Lang Chain or Lang Graph awareness (you won't write Python, but you will integrate with a Python AI service)
• Public‑cloud cost‑control habits