Next.js Performance Testing: A Practical Guide with k6

When building server-side rendered (SSR) applications with Next.js, it's essential to ensure they can handle heavy traffic without compromising performance. Load testing helps identify performance bottlenecks and optimize server response times.

Environment Setup used to load test (Will vary with different users)

Application Stack:

• Next.js (for SSR)

• AWS ECS (T3.medium) (for hosting)

Installing K6

MacOS

brew install k6

Linux

sudo apt install k6

Windows

choco install k6

Now, create a test.js file

import http from 'k6/http';
import { sleep, check } from 'k6';

const pages = [
  'https://your-nextjs-app.com/',
  'https://your-nextjs-app.com/about',
  'https://your-nextjs-app.com/contact',
  'https://your-nextjs-app.com/products',
];

const loadTest = () => {
  pages.forEach((page) => {
    const res = http.get(page);
    check(res, {
      'status is 200': (r) => r.status === 200,
      'response time < 200ms': (r) => r.timings.duration < 200,
    });
  });
  sleep(1);
}

export default loadTest;

Run the file

k6 run test.js

Analyze the result in the terminal

You can see the analytics, which will define

• Response Time: Speed at which each page loads.

• Error Rate: Number of failed requests.

• Throughput: Requests handled per second.

Track CPU and memory usage on AWS ECS or EC2 servers for accurate performance metrics.

In Summary

Load testing your Next.js app with k6 helps you check how well it handles lots of visitors. k6 is easy to use, lightweight, and works great with JavaScript. Just install it, write a simple script, and run the test to see how your app performs under pressure.