Performance monitoring basics in Express

Introduction

Performance monitoring helps you see how well your app runs. It shows if your app is slow or uses too much memory.

You want to check if your website loads fast for users.

You notice your app crashes or slows down sometimes.

You want to find parts of your app that use too much CPU or memory.

You want to improve user experience by fixing slow responses.

You want to track app health over time to avoid surprises.

Syntax

Express

const express = require('express');
const app = express();

// Use a middleware to measure response time
app.use((req, res, next) => {
  const start = Date.now();
  res.on('finish', () => {
    const duration = Date.now() - start;
    console.log(`${req.method} ${req.url} took ${duration}ms`);
  });
  next();
});

This example uses middleware to measure how long each request takes.

It logs the method, URL, and time in milliseconds after the response finishes.

Examples

Basic middleware to log request time for every HTTP request.

Express

app.use((req, res, next) => {
  const start = Date.now();
  res.on('finish', () => {
    const duration = Date.now() - start;
    console.log(`${req.method} ${req.url} took ${duration}ms`);
  });
  next();
});

Simple route to test the performance middleware.

Express

app.get('/', (req, res) => {
  res.send('Hello World!');
});

Sample Program

This program starts a server on port 3000. It logs how long each request takes. When you visit the homepage, it responds with 'Hello World!'.

Express

const express = require('express');
const app = express();

app.use((req, res, next) => {
  const start = Date.now();
  res.on('finish', () => {
    const duration = Date.now() - start;
    console.log(`${req.method} ${req.url} took ${duration}ms`);
  });
  next();
});

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(3000, () => {
  console.log('Server running on http://localhost:3000');
});

Important Notes

Performance times may vary depending on your computer speed.

Use this simple method to find slow routes or middleware.

For more detailed monitoring, consider tools like New Relic or Prometheus.

Summary

Performance monitoring shows how fast your app responds.

Middleware can measure request time easily in Express.

Logging response times helps find slow parts to improve.