Hire Node.js developers, from $1,500 a month

A senior Node.js developer is a backend engineer first. Expect them to talk through eight areas from their own production work.

• API design. REST resources, versioning, pagination, one error format, written docs. Our development service also lists GraphQL, but no project on this page depends on it, so put it in the brief and test for it.
• Frameworks. The same service lists Express.js and NestJS. Express calls itself a fast, unopinionated, minimalist web framework. NestJS is built with TypeScript, uses Express under the hood and supplies an application architecture out of the box.
• Relational data. PostgreSQL sits behind five of the six Qilin Lab projects in the next section. Expect schema design, migrations, indexes and transactions, not only ORM calls.
• Caching and search. Redis is on our service list. Elasticsearch is in the stack of the EcoProcurer solar marketplace below.
• Queues. RabbitMQ carries the ICS Mobile messaging pipeline below, and Kafka the Spend The Bits payments core. Expect fluency in acknowledgements, retries, dead letters and ordering.
• Auth. Sessions or tokens, OAuth, role-based access (the Canco admin portal applies it across 200+ stations) and per-tenant rate limits (ICS Mobile).
• Observability. Structured logs with request IDs, metrics, traces, alerts. ICS Mobile and Spend The Bits run on Prometheus and Grafana.
• Deployment. Docker, CI/CD, Kubernetes, AWS. All six projects run on AWS, four of them on Kubernetes.

Nobody is equally deep in all eight. Name the two or three that matter most in your brief.

Looking for a Node.js job? This page is for companies that buy developer capacity on contract. Qilin Lab's own hiring is on the careers page.

A contract backend developer works when the work is defined and someone technical directs it. It fails when you expect the contractor to supply both.

It fits when

• You have a backlog, a CTO or tech lead who reviews pull requests, and too few backend hands. You want another engineer in about a week, not after a salaried search.
• The work has edges: a new service, a payment or carrier integration, a module pulled out of a monolith, a move to a supported Node.js release, a queue in front of a slow dependency.
• You need cover for a period: parental leave, a launch, a client deadline, or a workload you cannot yet tell will last.

It does not fit when

• Nobody on your side can set priorities or judge backend work. If you want a team that owns delivery end to end, that is a project engagement; see development services. If someone technical does direct the work and you are weighing this against outsourcing or a dedicated team, the staff augmentation page sets it against managed services, outsourcing, a dedicated team and an in-house hire.
• You want a permanent employee with equity, in your office. Hire locally, and budget with the salary table below.
• The task is two weeks long. The unit here is a month of one person's full-time work. An hourly freelancer suits a small job better.
• Your contracts or regulator bar access from outside your country. Check before you brief anyone offshore.
• The heavy part is model training or numerical computing. That is Python work; see AI and ML engineers.

Three days shows how someone works, not whether their architecture holds. The month-to-month term and the replacement guarantee cover that, not the trial.

1. One request runs a 2-second CPU job. What happens to every other request?

They wait. Node.js runs your JavaScript on one event loop and hands file I/O, dns.lookup(), some crypto and zlib to a worker pool, as its guide on not blocking the event loop explains. That libuv pool defaults to 4 threads. A strong answer names the fix: chunk the work so it yields, or move it to worker threads, which the docs recommend for CPU-intensive JavaScript and not for I/O.

2. You stream a 5 GB export to a slow client. What keeps memory flat?

Backpressure. Per the Node.js streams guide, .write() returns false once the buffer passes highWaterMark, and the source pauses until 'drain' fires. The stream API reference sets that default at 64 KiB for byte streams on non-Windows platforms since v22.0.0. Good candidates use stream.pipeline(), which forwards errors and cleans up. The best carry the idea to queues: RabbitMQ's documentation pairs manual acknowledgements with a bounded prefetch.

3. A payment webhook arrives twice, and the copies overlap. Walk me through your handler.

Stripe's webhook documentation says an endpoint may receive an event more than once, order is not guaranteed, the signature check needs the raw body, and a 2xx should go back before slow logic. So: verify on the raw body (in Express, keep the JSON parser off that route), insert the event ID under a unique constraint in the same PostgreSQL transaction as the state change, acknowledge, then work from a queue. Outbound, send an idempotency key so a retry cannot charge twice.

4. Forty pods each open a pool of 20 PostgreSQL connections. What breaks?

Arithmetic: 800 connections against a server whose max_connections default is typically 100. A senior engineer sizes each pool from the database's limit or puts a pooler in front. They know the node-postgres pooling rules: a new connection costs a 20-30 millisecond handshake, one client runs one query at a time, and a client never released drains the pool for good. And a transaction stays on one checked-out client, never on pool.query.

5. Kubernetes sends your pod SIGTERM during a deploy. What happens next?

The Kubernetes pod lifecycle page gives a grace period, 30 seconds by default, then KILL. In Node.js, installing a SIGTERM listener removes the default exit, so the process must end itself. Expected sequence: fail readiness, call server.close() (it stops new connections and, since v19.0.0, closes idle keep-alive ones), stop consuming from the queue, let in-flight requests finish, close the database pool, exit. A timer shorter than the grace period is the backstop.

6. A list endpoint returns 50 orders and makes 51 queries. Find it and fix it.

The N+1 query. Senior engineers find it in query logs or a trace, not by reading code, and fix it with a join or one batched lookup such as WHERE id = ANY($1). They know ORMs hide it behind lazy loading, and they add a query-count assertion to the tests.

7. A promise rejects and nothing catches it. What happens, and what do you retry?

Since v15.0.0 the default --unhandled-rejections mode is throw: with no handler, the rejection is raised as an uncaught exception, which ends the process. Strong candidates separate operational errors (a timeout, a 503) from bugs. They retry only idempotent operations, with capped backoff and jitter, and park poison messages after a set number of attempts. RabbitMQ's documentation warns that consumers which requeue on every transient failure create a redelivery loop.

Node.js facts were checked on nodejs.org on 21 September 2026.

• With React. Four of the six projects above pair a Node.js API with a React front end. When both sides are TypeScript, request and response types can be shared, so a contract change fails the build before it reaches a user. If the backlog is mostly interface work, start with React developers.
• With Next.js. qilinlab.com is a Next.js 14 App Router site built by this team. Queues, long-running jobs and payment webhooks tend to outgrow a Next.js server and move into a separate Node.js service. If the site is the larger share of the work, see Next.js developers.
• One person for both ends. A small product with one API and one web app may not need a backend specialist. A full-stack developer starts at the same $1,500 a month.
• TypeScript on the server. The Node.js TypeScript page marks type stripping stable from v25.2.0 and v24.12.0. Node.js runs files with erasable TypeScript syntax directly and performs no type checking, so tsc still belongs in CI.
• Runtime version. The Node.js release page says production applications should use only Active LTS or Maintenance LTS releases. On 21 September 2026 it showed v24 and v22 as LTS, v26 as Current and v20 as end-of-life. An API on v20 or older has an upgrade to schedule, which makes a contained first project for a new backend engineer.