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.

First 90 days

• Read and document the existing BFF codebase alongside the outgoing engineering team
• Produce a quality baseline: test coverage, TypeScript 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

Ongoing

• 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 TypeScript — 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
• GraphQL or schema federation comfort (not required to be primary stack)
• MongoDB 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, ElastiCache
• CI/CD on GitHub 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
• WebSocket / WSS (the AI chat surface uses streaming)
• OpenAPI / Swagger contract-first workflows
• Prior gateway / aggregator / BFF role
• LangChain or LangGraph awareness (you won't write Python, but you will integrate with a Python AI service)
• Public-cloud cost-control habits