Sliding Rate Limiter

A production-ready TypeScript sliding window rate limiter for Node.js applications.

Supports:

• ✅ Sliding Window Algorithm
• ✅ Memory Store
• ✅ Redis Store
• ✅ Express Middleware
• ✅ TypeScript Support
• ✅ Custom Storage Adapters
• ✅ Rate Limit Headers
• ✅ ESM + CommonJS builds
• ✅ Fully Tested

Installation

Install using npm:

npm install sliding-rate-limiter

or using yarn:

yarn add sliding-rate-limiter

or pnpm:

pnpm add sliding-rate-limiter

Basic Usage

SlidingWindow

The core limiter can be used without Express.

import { SlidingWindow } from "sliding-rate-limiter";


const limiter = new SlidingWindow({

  max: 5,

  windowMs: 60000

});


async function test(){

  const result = await limiter.consume(
    "user-123"
  );


  console.log(result);

}


test();

Output:

{
  "allowed": true,
  "remaining": 4,
  "limit": 5,
  "retryAfter": 0,
  "resetAt": 1785257675953
}

Configuration

new SlidingWindow({

  max: 100,

  windowMs: 60000

});

Options

| Option | Type | Description | | -------- | ------ | --------------------------- | | max | number | Maximum requests allowed | | windowMs | number | Time window in milliseconds | | store | Store | Custom storage adapter |

Example:

{
  max: 10,
  windowMs: 10000
}

Allows:

10 requests every 10 seconds

Express Middleware

Protect your Express routes.

Install Express:

npm install express

Example:

import express from "express";

import {
  rateLimiter
} from "sliding-rate-limiter";


const app = express();


const limiter = rateLimiter({

  max: 5,

  windowMs: 60000

});


app.use(limiter);


app.get("/", (req,res)=>{

  res.json({

    message:"Request allowed"

  });

});


app.listen(3000);

Response Headers

Every request receives rate limit headers:

RateLimit-Limit
RateLimit-Remaining
RateLimit-Reset

Example:

RateLimit-Limit: 5

RateLimit-Remaining: 2

RateLimit-Reset: 1785260130942

When limit is exceeded:

HTTP 429 Too Many Requests

Response:

{
  "success": false,
  "message": "Too many requests. Please try again later.",
  "retryAfter": 60
}

Header:

Retry-After: 60

Multiple Users

Each key has its own limit.

Example:

await limiter.consume("user-1");

await limiter.consume("user-2");

Output:

user-1
Request 1 allowed
Request 2 allowed
Request 3 blocked


user-2
Request 1 allowed

Reset Limits

You can manually reset a user's rate limit.

await limiter.reset(
  "user-123"
);

After reset:

{
 allowed:true
}

Memory Store

Default storage.

No setup required.

Example:

import {
 SlidingWindow
} from "sliding-rate-limiter";


const limiter =
new SlidingWindow({

 max:10,

 windowMs:60000

});

Data is stored in application memory.

Useful for:

• Development
• Small applications
• Single server deployments

Redis Store

Redis support is available for distributed applications.

Install Redis client:

npm install ioredis

Example:

import Redis from "ioredis";

import {
 SlidingWindow,
 RedisStore
} from "sliding-rate-limiter";


const redis =
new Redis();


const limiter =
new SlidingWindow({

 max:100,

 windowMs:60000,


 store:
 new RedisStore(redis)

});

Redis allows:

• Multiple servers
• Horizontal scaling
• Shared rate limits

Custom Storage

You can create your own storage adapter.

Extend:

import {
 Store
} from "sliding-rate-limiter";


class CustomStore extends Store {


 async get(key:string){

 }


 async add(
  key:string,
  timestamp:number
 ){

 }


 async removeExpired(
  key:string,
  before:number
 ){

 }


 async count(
  key:string
 ){

 }


 async delete(
  key:string
 ){

 }


}

Then:

const limiter =
new SlidingWindow({

 max:10,

 windowMs:60000,

 store:new CustomStore()

});

Algorithm

This library uses the Sliding Window algorithm.

Flow:

Request
   |
   v
Remove expired timestamps
   |
   v
Count active requests
   |
   v
Check limit
   |
   +---- Allowed
   |
   +---- Blocked (429)

Example:

Window: 60 seconds

Limit: 5 requests


00s  Request
10s  Request
20s  Request
30s  Request
40s  Request


45s  Request blocked


70s
First request expires


New request allowed

Testing

Clone repository:

git clone <repository-url>

Install:

npm install

Run tests:

npm test

Example output:

✓ SlidingWindow.test.ts
✓ MemoryStore.test.ts
✓ RedisStore.test.ts
✓ Express.test.ts

10 tests passed

Building From Source

Install dependencies:

npm install

Build:

npm run build

Creates:

dist/

├── index.js
├── index.cjs
├── index.d.ts
└── source maps

Requirements

• Node.js >= 18
• TypeScript >= 5

Use Cases

Perfect for:

• API protection
• Authentication endpoints
• Login throttling
• Public APIs
• SaaS applications
• Microservices
• Distributed systems

Open Source

License

MIT License

Author

Hamza Ashfaq