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Explain how clustering works in Node.js.

Q: Explain how clustering works in Node.js.

**TL;DR.** The cluster module forks **multiple worker processes** (typically one per CPU core) that **share the same server port**. A primary process load-balances incoming connections across workers, so a single-threaded Node app can use **all cores** and survive a worker crash. primary :3000 worker (core 1) <rect class='d-box' x='180' y='107' width

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This question assesses understanding of how Node.js leverages multi-core CPUs despite its single-threaded nature.

clusteringscalabilityconcurrencyperformance

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Fork one worker per core

import cluster from 'node:cluster';
import { cpus } from 'node:os';
import http from 'node:http';

if (cluster.isPrimary) {
  for (let i = 0; i < cpus().length; i++) cluster.fork();
  cluster.on('exit', () => cluster.fork());      // restart on crash
} else {
  http.createServer((req, res) => res.end('hi from ' + process.pid))
      .listen(3000);                              // all share :3000
}

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