How to implement rate limiting in express app

Rate limiting is a technique used to control the amount of incoming traffic to a web server, ensuring fair usage and protecting the server from being overwhelmed by too many requests in a short period of time. In an Express.js application, you can implement rate limiting using middleware. One of the most popular middleware libraries for this purpose is express-rate-limit.

Here’s how you can implement rate limiting in an Express app:

Step-by-Step Guide to Implement Rate Limiting

1. Install the express-rate-limit package:

   First, you need to install the express-rate-limit package using npm:

   npm install express-rate-limit
   

2. Set up the rate limiting middleware:

   Create a rate limiter using express-rate-limit and apply it to your Express app. Here’s an example:

   const express = require('express');
   const rateLimit = require('express-rate-limit');
   
   const app = express();
   
   // Create a rate limiter
   const limiter = rateLimit({
     windowMs: 15 * 60 * 1000, // 15 minutes
     max: 100, // Limit each IP to 100 requests per `window` (here, per 15 minutes)
     standardHeaders: true, // Return rate limit info in the `RateLimit-*` headers
     legacyHeaders: false, // Disable the `X-RateLimit-*` headers
   });
   
   // Apply the rate limiter to all requests
   app.use(limiter);
   
   // Example routes
   app.get('/', (req, res) => {
     res.send('Welcome to the home page!');
   });
   
   app.get('/api', (req, res) => {
     res.send('Welcome to the API!');
   });
   
   // Start the server
   const PORT = process.env.PORT || 3000;
   app.listen(PORT, () => {
     console.log(`Server is running on port ${PORT}`);
   });
   

3. Customizing the rate limiter:

   You can customize the rate limiter according to your needs. Here are some common options:

   • windowMs: The time window for which requests are tracked. In the example above, it’s set to 15 minutes.
   • max: The maximum number of requests allowed from a single IP within the time window. In the example above, it’s set to 100.
   • message: The response body to send back when a client hits the rate limit.
   • statusCode: The status code to return when the rate limit is exceeded (default is 429).
   • headers: Controls whether to include rate limit headers in the response.

   Here’s an example with some custom settings:

   const customLimiter = rateLimit({
     windowMs: 10 * 60 * 1000, // 10 minutes
     max: 50, // Limit each IP to 50 requests per 10 minutes
     message: 'Too many requests from this IP, please try again after 10 minutes',
     statusCode: 429, // HTTP status code to send
   });
   
   // Apply the custom limiter to a specific route
   app.use('/api/', customLimiter);
   

4. Handling different routes differently:

   You can apply different rate limits to different routes or groups of routes by creating multiple instances of the rate limiter with different settings and applying them accordingly.

   const generalLimiter = rateLimit({
     windowMs: 15 * 60 * 1000, // 15 minutes
     max: 100,
   });
   
   const apiLimiter = rateLimit({
     windowMs: 5 * 60 * 1000, // 5 minutes
     max: 20,
     message: 'Too many requests to the API from this IP, please try again after 5 minutes',
   });
   
   // Apply the general limiter to all routes
   app.use(generalLimiter);
   
   // Apply the API limiter to API routes only
   app.use('/api/', apiLimiter);