node-rate-limiter-flexible

rate-limiter-flexible counts and limits the number of actions by key 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.

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

It uses a fixed window, as it is much faster than a rolling window. See comparative benchmarks with other libraries here

Installation

npm i --save rate-limiter-flexible

yarn add rate-limiter-flexible

Import

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

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

Basic Example

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
    });

RateLimiterRes object

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)
}

Advantages:

no race conditions
no production dependencies
TypeScript declaration bundled
Block Strategy against really powerful DDoS 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

Middlewares, plugins and other packages

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

Some copy/paste examples on Wiki:

Migration from other packages

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

Docs and Examples

Options
API methods
Drizzle Atomic and non-atomic counters.
DynamoDb
Etcd Atomic and non-atomic counters.
Memcached
Memory
Mongo (with sharding support)
MySQL (support Sequelize and Knex)
Postgres (support Sequelize, TypeORM and Knex)
Prisma
Redis
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
RateLimiterQueue Rate limiter with FIFO queue
AWS SDK v3 Client Rate Limiter Prevent punishing rate limit.

Changelog

See releases for detailed changelog.

Basic Options

points

Default: 4

Maximum number of points that can be consumed over duration
duration

Default: 1

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 @valkey/valkey-glide, iovalkey, redis, ioredis, memcached, mongodb, pg, mysql2, mysql or any other related pool or connection.

Other options on Wiki:

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.

API

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.

Contributions

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 depends on the store. See RateLimiterRedis or RateLimiterPostgres for examples.

Note: all changes should be covered by tests.