Node.js Backend Developer for Secure APIs and Firebase Backends

What a good backend does for your product

If your app is the shop front, the backend is the locked back office, where the important decisions happen out of reach of anyone poking around in their browser. When you hire a Node.js developer, this is what you are paying for. A backend does four jobs:

• It is your security boundary. Anything that runs in the browser can be read and changed by the person using it. The backend is the one place you control, so it is where you decide who is signed in and what they are allowed to do.
• It enforces your business rules. Prices, discounts, usage limits, who can approve what. If these rules only live in the frontend, someone can bypass them with a few minutes of effort.
• It protects your data. A good backend checks every request before it reaches the database, so you do not end up with half-saved orders, duplicate accounts or records that no longer match.
• It connects you to other services. Payments, email, AI models and other third-party APIs need secret keys. The backend holds those keys and makes the calls on your behalf.

I have built this kind of backend logic in production: for timegram, a privacy-first time-tracking SaaS, and for Atompoint's Global School Payment platform, both built with Node.js and Firebase, where I worked on the user interface and the backend logic behind it.

What I build

REST APIs with Express

Most of my Node.js API development uses Express (opens in a new tab), a lightweight and widely used framework for building APIs on Node.js (opens in a new tab). An Express REST API is a set of clear addresses (endpoints) your app calls to read and change data, such as "create an order" or "list this customer's invoices". I write them in TypeScript and organise the code so each part has one job.

Firebase and Firestore backends

If your product runs on Firebase, I work as a Firebase backend developer: designing your Firestore data structure, writing security rules, and moving sensitive logic into Cloud Functions (opens in a new tab), small pieces of server code that run when something happens, such as a new sign-up or a completed payment.

Data, accounts and integrations

• MongoDB and Firestore data models designed around how your app actually reads and writes data.
• Authentication and authorisation: sign-in, user roles, and server-side checks on every request.
• Payments, email and webhooks: connecting payment providers, transactional email and notifications that other services send to your app.
• Scheduled and background jobs: reminders, reports, clean-ups and anything that should run on a timer rather than while a user waits.

Moving logic out of the browser

This is one of the most common problems I see, especially in apps built quickly with AI coding tools. The prototype works, but the browser talks directly to OpenAI, Stripe or the database, with secret keys bundled into the code anyone can download.

The fix is to put a thin, secure API between your app and those services. The frontend asks your backend to do something; the backend checks who is asking, validates the request, applies your rules and only then calls the outside service. If your app was built with AI tools and you are not sure how exposed it is, my AI app production-ready service covers exactly this, and a fixed-price production audit will tell you what needs fixing first.

How I build APIs you can trust

A backend that works in a demo is not the same as one you can trust with real customers. On every project I include:

• Validation: every request is checked for the right shape and sensible values before it touches your data.
• Consistent error handling: users see helpful messages, while the technical details go to your logs rather than to the screen.
• Logging: so that when something goes wrong, we can see what happened instead of guessing.
• Rate limiting: limits on how often one person can hit sensitive endpoints such as sign-in or AI features, which protects you from abuse and surprise bills.
• Tests for critical paths: sign-in, permissions, payments and anything that changes important data.
• Documentation: a written description of each endpoint, often in the OpenAPI format, plus a Postman collection your team can use to try the API.

I follow widely accepted security guidance such as the OWASP API Security Top 10 (opens in a new tab). I use AI tools such as Claude Code daily to work faster, and I review every line they produce with the same rigour as code written by hand.

Deployment and handover

When the backend is ready, I deploy it to your own hosting or Firebase account, set up secrets properly, and test it end to end with your frontend. You get the source code in your repository, deployment notes, the API documentation and a walkthrough call, so you never depend on me to keep things running.

Because I also build frontends, I can make sure the API fits the screens that use it; see my Next.js development service if you need both. You can find project rates on the pricing page, or get in touch to talk through what your backend needs to do.