Hire Node.js Developers

Start with the event loop. A strong Node.js developer can explain why a synchronous JSON.parse on a large payload, a tight CPU loop or a blocking crypto call stalls every request on the process, and knows the fixes - streaming parsers, worker threads, moving heavy work to a queue, or splitting the service. Ask how they would detect event-loop lag in production, not just define it.

Async fluency is the next filter: promises and async/await without unhandled rejections, bounded concurrency instead of an unthrottled Promise.all over thousands of items, cancellation with AbortController, and back-pressure when piping streams. Expect TypeScript as the default, with strict mode on and typed boundaries at the API and database layers rather than any scattered through the code.

Framework judgement matters more than framework loyalty. Express suits small, explicit services; NestJS brings modules, dependency injection and conventions that help larger teams; Fastify is a common choice where raw throughput counts. Finally, look for performance profiling habits - flame graphs from the built-in inspector or clinic-style tooling, heap snapshots to chase memory leaks, and load tests that reproduce the problem before anyone tunes it.

The first weeks are usually about the existing codebase: getting the service running locally, reading the API contracts, reviewing error handling and logging, and fixing small issues to learn the deployment path. A good hire will surface risks early - outdated dependencies with known vulnerabilities, missing input validation, N+1 database queries, or endpoints with no timeouts on downstream calls.

After that, responsibilities typically shift to feature delivery and hardening: building new endpoints or services, adding integration tests around critical flows such as payments and authentication, introducing structured logs and request tracing, and tightening connection pooling and caching with Redis. By the end of the first quarter you should expect them to own a slice of the backend end to end, including its on-call runbook notes and performance baselines.

A dedicated developer suits an evolving product: an API that changes every sprint, a backlog shared with your own team, and knowledge you want retained over time. Project-based delivery suits a bounded outcome - a new microservice, a migration from callbacks or plain JavaScript to TypeScript, a REST-to-GraphQL layer, or a performance remediation with a clear finish line.

Decide by asking whether the scope is stable enough to price as milestones. If it is, project-based work with milestone-based pricing keeps costs transparent; if requirements will keep moving, a dedicated engagement avoids repeated re-scoping. Either way, the client owns the code and IP, and an NDA is signed before kickoff.

Skip algorithm puzzles and test the work the role actually involves. A practical format is a short take-home or paired session on a small TypeScript API: add an endpoint with validation, call a slow downstream service with a timeout and retry, write a test for the failure path, and explain how they would page through a large result set without loading it all into memory.

Follow up with a code review exercise. Hand the candidate a snippet with a blocking call inside a request handler, a missing await, and an unbounded loop of database queries, and see what they spot and how they prioritise. Close with a design conversation about one of your real problems - queue versus synchronous call, where to cache, how to roll out a breaking API change - which shows judgement better than any quiz.