| name | rate-limiter-flexible |
| description | Use this skill whenever working with rate limiting, brute-force protection, DoS mitigation, or the `rate-limiter-flexible` npm package in Node.js. Triggers include: mentions of 'rate limit', 'rate-limiter-flexible', 'RateLimiter', 'brute force protection', 'login endpoint protection', 'too many requests', '429', throttling in Node.js, or configuring limiters with Redis/Mongo/MySQL/PostgreSQL/Memory/Memcached/DynamoDB/Drizzle/Prisma/SQLite/Cluster/PM2/Etcd/Valkey. Also trigger when writing Express/Koa/Hapi middleware for request limiting, or protecting APIs and websockets from flooding. Use this skill even for tangential questions about rate limiting architecture, choosing a store backend, or scaling rate limiters in distributed systems. |
rate-limiter-flexible
Harden application security against brute-force and DoS attacks.
Atomic and non-atomic counters and rate limiting tools for Node.js, Deno, and browsers (Memory limiter). Zero production dependencies. Enhanced fixed window algorithm. ISC license.
- Install:
npm i rate-limiter-flexible
- ESM:
import { RateLimiterMemory } from "rate-limiter-flexible"
- CommonJS:
const { RateLimiterMemory } = require("rate-limiter-flexible")
When to Use This Skill
- Configuring any
rate-limiter-flexible limiter (options, API, store setup)
- Writing Express/Koa/Hapi rate limiting middleware
- Implementing login brute-force protection or DoS mitigation
- Choosing between store backends (Redis vs Memory vs Mongo vs etc.)
- Setting up insurance strategy, in-memory block strategy, or BurstyRateLimiter
- Understanding
RateLimiterRes object and HTTP response headers
Quick Reference
See references/full-reference.md for the complete guide covering:
- All options (common + store-specific) with defaults
- All API methods (
consume, get, set, block, delete, penalty, reward, deleteInMemoryBlockedAll)
RateLimiterMemory best-effort persistence via dump() / restore() (snapshot state for graceful restarts)- All 15+ limiter types (Redis, Memory, Mongo, MySQL, PostgreSQL, DynamoDB, Memcached, Prisma, Drizzle, SQLite, Etcd, Valkey, Cluster, PM2)
- Composite limiters (BurstyRateLimiter, RateLimiterUnion, RateLimiterQueue)
- Wrappers (Black/White lists, Timeouts, AWS SDK v3)
- Code examples for every common pattern
Essential Patterns at a Glance
Basic Usage
const { RateLimiterMemory } = require("rate-limiter-flexible");
const limiter = new RateLimiterMemory({
points: 10,
duration: 1,
});
limiter.consume(req.ip)
.then((res) => { })
.catch((res) => {
if (res instanceof Error) { }
else { }
});
HTTP Response Headers
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)
};
Key Defaults
| Option | Default | Notes |
|---|
points | Required | Max consumable over duration |
duration | Required | Seconds before reset; 0 = never expire |
keyPrefix | 'rlflx' | Must be unique per limiter |
blockDuration | 0 | Seconds to block after points exhausted |
Links
