🚀 API Rate Limiter (Node.js)

A simple, customizable API Rate Limiter middleware for Node.js and Express.

Supports multiple rate limiting algorithms and is designed to be easy to use, plug-and-play, and beginner-friendly.

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✨ Features

• ✅ Multiple Algorithms:
  • Fixed Window
  • Sliding Window
  • Token Bucket
  • Leaky Bucket
• ✅ Plug-and-play middleware
• ✅ Custom key generation (IP / user / headers)
• ✅ Rate limit headers support
• ✅ Lightweight (no external dependencies)
• ✅ Easy configuration

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📦 Installation

Clone the repository:

git clone https://github.com/YOUR_USERNAME/api-rate-limiter.git
cd api-rate-limiter
npm install

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⚙️ Basic Usage

Create a simple Express server:

const express = require("express");
const rateLimiter = require("./index");

const app = express();

// Apply rate limiter
app.use(rateLimiter({
    type: "fixedWindow",
    limit: 5,
    window: 10, // seconds
    headers: true
}));

app.get("/", (req, res) => {
    res.send("Working!");
});

app.listen(3000, () => {
    console.log("Server running on port 3000");
});

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🧪 Testing the Rate Limiter

Run your server:

node test.js

Then send multiple requests:

curl -i http://localhost:3000

After exceeding the limit, you’ll get:

{
  "message": "Too many requests, please try again later."
}

📊 Rate Limit Headers

When enabled (headers: true), responses include:

X-RateLimit-Limit: 5
X-RateLimit-Remaining: 2
Retry-After: 5

These headers help clients understand usage and retry timing.

⚙️ Configuration Options

Option	Description	Default
type	Algorithm type	"tokenBucket"
limit	Max requests	10
window	Time window (seconds)	60
message	Error message	"Too many requests..."
statusCode	HTTP status	429
headers	Enable headers	true
keyGenerator	Custom key function	req.ip
store	Custom storage	Memory store

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🔀 Supported Algorithms

1. Fixed Window

• Simple and fast
• Resets after time window

2. Sliding Window

• More accurate than fixed window
• Prevents burst abuse

3. Token Bucket

• Allows bursts
• Smooth refill over time

4. Leaky Bucket

• Constant request rate
• Best for steady traffic

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🔑 Custom Key Generator

You can rate limit per user instead of IP:

app.use(rateLimiter({
    limit: 5,
    keyGenerator: (req) => req.headers["user-id"]
}));

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📁 Project Structure

API-RateLimiter/
│── algorithms/
│── middleware/
│── store/
│── utils/
│── config/
│── index.js

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🧠 How It Works

Rate limiting helps prevent abuse and ensures system stability by restricting how many requests a client can make in a given time window.

This project:

• Tracks requests per user/key
• Applies chosen algorithm
• Blocks requests when limit is exceeded

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🚀 Future Improvements

• Redis support (for distributed systems)
• API key-based rate limiting
• Dashboard for monitoring
• npm package publishing