How to optimize Node.js performance?

# CPU profiling
node --prof app.js
node --prof-process isolate-*.log > profile.txt

# Using clinic.js
npx clinic doctor -- node app.js
npx clinic flame -- node app.js

const cluster = require('cluster');
const os = require('os');

if (cluster.isMaster) {
  for (let i = 0; i < os.cpus().length; i++) {
    cluster.fork();
  }
} else {
  require('./app');
}

const cache = new Map();

function getCachedData(key, fetchFn, ttl = 60000) {
  const cached = cache.get(key);
  if (cached && Date.now() < cached.expires) {
    return cached.data;
  }

  const data = fetchFn();
  cache.set(key, { data, expires: Date.now() + ttl });
  return data;
}

// ❌ Blocks event loop
const data = fs.readFileSync('large-file.txt');

// ✅ Non-blocking
const data = await fs.promises.readFile('large-file.txt');

// ❌ CPU-intensive in main thread
const hash = crypto.pbkdf2Sync(password, salt, 100000, 64, 'sha512');

// ✅ Use worker or async
const hash = await new Promise((resolve, reject) => {
  crypto.pbkdf2(password, salt, 100000, 64, 'sha512', (err, key) => {
    if (err) reject(err);
    else resolve(key);
  });
});

// ❌ Load all into memory
app.get('/file', (req, res) => {
  const data = fs.readFileSync('large-file.txt');
  res.send(data);
});

// ✅ Stream
app.get('/file', (req, res) => {
  fs.createReadStream('large-file.txt').pipe(res);
});