A guide to hiring an Express.js developer
Express is a small, widely used web framework for Node.js. It gives a Node.js program a clean way to receive web requests, route each one to the right code and send back a response. Many APIs, web back ends and the server side of JavaScript products are built on it. This guide explains what an Express.js developer does, how the role differs from a general Node.js developer, and how to test and work with one. It is written for founders and engineering managers who already know they need an Express back end or want to extend one.
What an Express.js developer is responsible for
An Express.js developer writes and looks after the server code that your app or website talks to. That includes the routes that handle each request, the middleware that runs before them, the checks on incoming data and the error handling that decides what a user sees when something goes wrong. They connect the server to a database, protect private routes, add logging and write the tests that stop old faults from coming back. In a small team the same person may also deploy the service and watch it after release.
Routing and middleware, in plain words
Routing means matching a web address and method, such as a request to read an order, with the function that handles it. Middleware is code that sits in the chain before or after the route. Typical jobs for middleware are reading a login token, limiting how many requests one visitor can make, checking the shape of the data and writing a log line. A good Express developer keeps routes thin, puts shared steps in middleware and keeps the order of that chain clear, since the order decides what runs first.
How this role differs from a Node.js developer
Express runs on Node.js, so every Express developer knows Node.js. The reverse is not always true. A Node.js developer may work on real-time features, workers, command-line tools or other frameworks, and may never have shaped a large Express application. Use the Express page when your server already uses Express, or when the main job is a REST API with routes, middleware and a database. Use the Node.js page when you need the wider runtime skill set, or are still choosing a framework.
Where Express fits
- You are building or extending a REST API for a web or mobile app.
- You run the server side of a MERN project, where Express sits between React and MongoDB. See our MERN developers.
- You want a small, flexible server without a large framework’s rules.
- You have an older Express app that needs tests, cleaner structure or upgrades.
If you want a framework with strong built-in structure for a very large team, a developer who knows another framework may suit you better. A fair candidate will say so.
What to look for in a background
Look for Express code that served real users, not tutorials. Ask which routes they wrote, how the project was laid out and what failed in production. Strong answers describe a fault, its cause and what was done about it. Be careful with a resume that lists a dozen frameworks in one line and no detail. Ask the candidate to talk through one bug they traced from a user report back to a line of code.
Interview questions to try
- How is middleware ordered in one of your Express apps, and why in that order?
- How do you handle errors so a failure in one route does not crash the server?
- How do you check incoming data, and where does that check live?
- Tell us about a slow endpoint you fixed. What did you measure first?
- How would you protect a route so only logged-in users can use it?
Listen for specific stories and clear trade-offs. Be wary of anyone with the same answer for every question.
Try a paid mini project
Hand each finalist a small job drawn from your own product. Options include a short API with three routes, input checks and tests, a read-through of some of your Express code that ends in a list of risks, or a plan for breaking one huge route file into parts. Pay for the time. Judge the readability, the tests and how the person explains their decisions to a non-specialist.
Security habits worth asking about
A server on the open internet needs care. Ask how the candidate stores passwords, how they keep secrets out of the code, how they limit requests from one visitor and how they set safe response headers. Ask about handling uploads and about keeping packages up to date. You are not looking for a lecture, only for signs that the person has done this before and thinks about it as part of the job.
Agree access and routine
Fix the weekly hours at the outset. The developer should have personal logins for the repository, the build tool and the test servers, while the cloud and domain accounts stay in your company’s name. Ask for a brief write-up with each change, including how to reverse it, so handovers go smoothly. Close the accounts when the work is done.
Mistakes to avoid
- Putting all the logic inside route handlers until nobody can test it.
- Skipping input checks because the front end already checks the form.
- Leaving secrets and passwords in the code repository.
- Letting one contractor hold the only key to your server or cloud account.
Not sure Express is the right pick? Compare it with our API developers, or read about our back-end developers if the language is still open.