How to Build APIs with Node.js and Fastify

Why Choose Fastify?

Fastify is popular in the Node.js ecosystem due to its performance and extensibility. This means developers can add more features without changing its core. In short, it provides a solid performance, and features like schema-based validation and a plugin system make development faster.

1. Fastify is one of the fastest Node.js frameworks.
2. Built-in support for JSON Schema validation for input handling.
3. Fastify's provides a modular development environment with its plugin-based architecture.
4. It includes hooks, decorators, and several other features to enhance productivity.
5. Compared to alternatives like Express, Fastify offers superior performance and a more structured approach to building APIs.

Setting Up a Fastify Project

Here's what it requires to create an API with Fastify.

1. Node.js (v16 or higher)
2. npm
3. A code editor (e.g., VS Code)

Step 1: Initialize a Node.js Project

Create a new directory for your project and initialize it:

Step 2: Install Fastify

npm install fastify

Step 3: Create a Basic Server

Create a file named server.js:

Run the server with:

This simple setup demonstrates Fastify's minimalistic approach to creating an API server.

Routing in Fastify

Fastify's routing system is intuitive and supports both synchronous and asynchronous handlers. Let's expand our API with more routes.

Example: User API

Create routes to manage a list of users. Update server.js:

Testing the Routes

Use a tool like Postman or curl to test the API:

Fastify's routing is clean and supports dynamic parameters, query strings, and various HTTP methods out of the box.

Schema Validation with Fastify

Fastify's JSON Schema support allows you to validate incoming requests and outgoing responses. This ensures data integrity and reduces boilerplate code.

Adding Validation

Update the POST /users route to include a schema:

Now, if you send an invalid request (e.g., missing name or invalid email), Fastify will return a 400 error:

This schema-based validation ensures robust input handling without manual checks.

Middleware and Hooks

Fastify uses hooks instead of traditional middleware for lifecycle management. Hooks allow you to execute code at various stages of the request-response cycle.

Example: Logging Middleware

Add a hook to log request details:

This logs every incoming request. Fastify supports hooks like onRequest, preHandler, onResponse, and more for granular control.

Example: Authentication Middleware

Simulate a simple API key check:

Test with curl:

curl http://localhost:3000/users -H "x-api-key: my-secret-key"

Without the correct API key, you'll get a 401 error.

Plugins for Modularity

Fastify's plugin system allows you to organize code into reusable modules. Let's create a plugin for user routes.

Step 1: Create a Plugin

Create users-plugin.js:

Step 2: Register the Plugin

Update server.js:

The routes are now modularized, making the codebase cleaner and easier to maintain.

Connecting to a Database

For a real-world API, you'll likely need a database. Let's integrate Fastify with MongoDB using the fastify-mongodb plugin.

Step 1: Install Dependencies

npm install fastify-mongodb mongodb

Step 2: Update the Plugin

Modify users-plugin.js to use MongoDB:

Step 3: Register MongoDB

Update server.js:

Ensure MongoDB is running locally, and create a database named fastify_db. The API now uses MongoDB for persistent storage.

Error Handling

Fastify provides built-in error handling. You can define custom error handlers to manage errors gracefully:

This ensures all uncaught errors return a consistent response format.

Deployment

To deploy your Fastify API, consider platforms like Heroku, AWS, or Vercel. Here's a quick guide for deploying to Vercel:

Install Vercel CLI:

Conclusion

Fastify, combined with Node.js, provides an efficient way to build APIs. Fastify is a popular choice when it comes to building lightweight APIs with Nodejs. In this guide, we have had a brief overview of how to create a Fastify project, create routes, establish a connection with the database, and deployment. If you are looking to modernize your existing app or want to build an app with top-rated Node.js developers, connect with us today to build a web application.