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Build a Custom Rate Limiter in Node.js with Redis

Tutorial April 04, 2025 

// rateLimiter.js
const client = require("./redisClient");

const rateLimiter = (limit = 100, windowSec = 3600) => {
  return async (req, res, next) => {
    const ip = req.ip;
    const key = `rate_limit:${ip}`;

    const current = await client.get(key);

    if (current !== null && parseInt(current) >= limit) {
      return res.status(429).json({ error: "Too many requests. Try later." });
    }

    const multi = client.multi();
    multi.incr(key);
    if (!current) {
      multi.expire(key, windowSec);
    }
    await multi.exec();

    next();
  };
};

module.exports = rateLimiter;
// server.js
require("dotenv").config();
const express = require("express");
const rateLimiter = require("./rateLimiter");

const app = express();
const PORT = 3000;

app.use(rateLimiter(100, 3600)); // 100 requests/hour per IP

app.get("/", (req, res) => {
  res.send("Welcome! You're within rate limit.");
});

app.listen(PORT, () => {
  console.log(`Server running on http://localhost:${PORT}`);
});

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