rate-limiter-flexible counts and limits the number of events and protects from DoS and brute force attacks at any scale.

It works with Valkey, Redis, Prisma, DynamoDB, process Memory, Cluster or PM2, Memcached, MongoDB, MySQL, SQLite, and PostgreSQL.

Memory limiter also works in the browser.

AI tools See llms.txt and CONTEXT.md for LLM-friendly documentation.

Atomic increments. All operations in memory or distributed environment use atomic increments against race conditions.

Fast. Average request takes 0.7ms in Cluster and 2.5ms in Distributed application. See benchmarks.

Flexible. Combine limiters, block key for some duration, delay actions, manage failover with insurance options, configure smart key blocking in memory and many others.

Ready for growth. It provides a unified API for all limiters. Whenever your application grows, it is ready. Prepare your limiters in minutes.

Friendly. No matter which node package you prefer: valkey-glide or iovalkey, redis or ioredis, sequelize/typeorm or knex, memcached, native driver or mongoose. It works with all of them.

In-memory blocks. Avoid extra requests to store with inMemoryBlockOnConsumed.

Deno compatible See this example

The Flexible Fixed Window algorithm starts counting from the moment a request is received, diversifying rate limit reset times across clients. Read more here

npm i --save rate-limiter-flexible

yarn add rate-limiter-flexible

import { RateLimiterMemory } from "rate-limiter-flexible";

// or import directly
import RateLimiterMemory from "rate-limiter-flexible/lib/RateLimiterMemory.js";

Points can be consumed by IP address, user ID, authorisation token, API route or any other string.

const opts = {
  points: 6, // 6 points
  duration: 1, // Per second
};

const rateLimiter = new RateLimiterMemory(opts);

rateLimiter.consume(remoteAddress, 2) // consume 2 points
    .then((rateLimiterRes) => {
      // 2 points consumed
    })
    .catch((rateLimiterRes) => {
      // Not enough points to consume
    });

The Promise's resolve and reject callbacks both return an instance of the RateLimiterRes class if there is no error. Object attributes:

RateLimiterRes = {
    msBeforeNext: 250, // Number of milliseconds before next action can be done
    remainingPoints: 0, // Number of remaining points in current duration 
    consumedPoints: 5, // Number of consumed points in current duration 
    isFirstInDuration: false, // action is first in current duration 
}

You may want to set HTTP headers for the response:

const headers = {
  "Retry-After": rateLimiterRes.msBeforeNext / 1000,
  "X-RateLimit-Limit": opts.points,
  "X-RateLimit-Remaining": rateLimiterRes.remainingPoints,
  "X-RateLimit-Reset": Math.ceil((Date.now() + rateLimiterRes.msBeforeNext) / 1000)
}

• no race conditions
• no production dependencies
• TypeScript declaration bundled
• Block Strategy against really powerful DoS attacks (like 100k requests per sec) Read about it and benchmarking here
• Insurance Strategy as emergency solution if database/store is down Read about Insurance Strategy here
• works in Cluster or PM2 without additional software See RateLimiterCluster benchmark and detailed description here
• useful get, set, block, delete, penalty and reward methods

Full documentation is on Wiki

• Express middleware
• Koa middleware
• Hapi plugin
• GraphQL graphql-rate-limit-directive
• NestJS nestjs-rate-limiter
• Fastify-based NestJS app try nestjs-fastify-rate-limiter

Copy/paste examples on Wiki:

• Minimal protection against password brute-force
• Login endpoint protection
• Apply Block Strategy
• Setup Insurance Strategy
• Websocket connection prevent flooding
• Dynamic block duration
• Authorized users specific limits
• Different limits for different parts of application
• Third-party API, crawler, bot rate limiting

• express-brute Bonus: race conditions fixed, prod deps removed
• limiter Bonus: multi-server support, respects queue order, native promises

• Options

• API methods

• Drizzle Atomic and non-atomic counters.

• DynamoDb

• Etcd Atomic and non-atomic counters.

• Memcached

• Memory Supports dump() and restore() for graceful restarts and green/blue deployment

• Mongo (with sharding support)

• MySQL (support Sequelize and Knex)

• Postgres (support Sequelize, TypeORM and Knex)

• Prisma

• Redis Atomic and non-atomic counters.

• SQLite

• Valkey: iovalkey or ValkeyGlide

• RateLimiterCluster (PM2 cluster docs read here)

• BurstyRateLimiter Traffic burst support

• RateLimiterUnion Combine 2 or more limiters to act as single

• RLWrapperBlackAndWhite Black and White lists

• RLWrapperTimeouts Timeouts

• RateLimiterQueue Rate limiter with FIFO queue

• AWS SDK v3 Client Rate Limiter Prevent punishing rate limit.

See releases for detailed changelog.

• points

  Required

  Maximum number of points that can be consumed over duration

• duration

  Required

  Number of seconds before consumed points are reset.

  Points are never reset if duration is set to 0.

• storeClient

  Required for store limiters

  Must be pool or connection created with store client packages, e.g. @valkey/valkey-glide, ioredis, iovalkey, redis, memcached, mongodb, pg, mysql2, mysql, etc.

• keyPrefix Make keys unique among different limiters.
• blockDuration Block for N seconds, if consumed more than points.
• inMemoryBlockOnConsumed Avoid extra requests to store.
• inMemoryBlockDuration
• insuranceLimiter Make it more stable with less efforts.
• storeType Have to be set to knex, if you use it.
• dbName Where to store points.
• tableName Table/collection.
• tableCreated Is table already created in MySQL, SQLite or PostgreSQL.
• clearExpiredByTimeout For MySQL, SQLite and PostgreSQL.

See full list of options.

Read detailed description on Wiki.

• consume(key, points = 1) Consume points by key.
• get(key) Get RateLimiterRes or null.
• set(key, points, secDuration) Set points by key.
• block(key, secDuration) Block key for secDuration seconds.
• delete(key) Reset consumed points.
• deleteInMemoryBlockedAll
• penalty(key, points = 1) Increase number of consumed points in current duration.
• reward(key, points = 1) Decrease number of consumed points in current duration.
• getKey(key) Get internal prefixed key.

Appreciated, feel free!

Make sure you've launched npm run eslint before creating PR, all errors have to be fixed.

You can try to run npm run eslint-fix to fix some issues.

Any new limiter with storage must be extended from RateLimiterStoreAbstract. It has to implement 4 methods:

• _getRateLimiterRes parses raw data from store to RateLimiterRes object.

• _upsert may be atomic or non-atomic upsert (increment). It inserts or updates the value by key and returns raw data. If it doesn't make an atomic upsert (increment), the class should be suffixed with NonAtomic, e.g. RateLimiterRedisNonAtomic.

  It must support forceExpire mode to overwrite key expiration time.

• _get returns raw data by key or null if there is no key.

• _delete deletes all key-related data and returns true on deleted, false if key is not found.

All other methods depend on the store. See RateLimiterRedis or RateLimiterPostgres for examples.

For wrapper classes that don't need full RateLimiterAbstract functionality, extend RateLimiterCompatibleAbstract instead. It requires implementing consume, penalty, reward, get, set, block, delete methods and blockDuration/execEvenly getters/setters. If the wrapper doesn't use blockDuration or execEvenly, empty no-op implementations can be provided. See RLWrapperBlackAndWhite for an example.

Note: all changes should be covered by tests.