Why caching is central to Next.js - Performance Evidence

Performance: Why caching is central to Next.js

HIGH IMPACT

Caching in Next.js affects page load speed and reduces server response time by reusing previously generated content.

Serving pages quickly in Next.js

NextJS

export async function getStaticProps() {
  const data = await fetch('https://api.example.com/data');
  const json = await data.json();
  return { props: { json }, revalidate: 60 };
}

// Static generation with incremental static regeneration caches page for 60 seconds

Page is prebuilt and cached, served instantly, and only regenerated periodically.

📈 Performance GainReduces server response time to under 50ms, lowers CPU load, improves LCP

Serving pages quickly in Next.js

NextJS

export async function getServerSideProps() {
  const data = await fetch('https://api.example.com/data');
  const json = await data.json();
  return { props: { json } };
}

// This runs on every request, no caching

Fetching data and rendering on every request causes slow response and high server load.

📉 Performance CostBlocks rendering for 200-500ms per request, increases server CPU usage

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Server-side rendering on every request	N/A	N/A	High due to slow server response	[X] Bad
Static generation with caching	N/A	N/A	Low due to fast server response	[OK] Good

Rendering Pipeline

Next.js caching avoids repeated server-side rendering by serving prebuilt HTML and JSON. This skips expensive data fetching and rendering during the critical rendering path.

→Server Rendering

→Network

→Browser Rendering

⚠️ BottleneckServer Rendering when no cache is used

Core Web Vital Affected

LCP

Caching in Next.js affects page load speed and reduces server response time by reusing previously generated content.

Optimization Tips

1Use static generation with caching to speed up page loads.

2Avoid server-side rendering on every request for better performance.

3Set revalidate times to balance freshness and speed.

Performance Quiz - 3 Questions

What is the main performance benefit of caching pages in Next.js?

A Larger JavaScript bundles

B More frequent server rendering

C Faster page load by serving prebuilt content

D Increased network requests

DevTools: Network

How to check: Open DevTools, go to Network tab, reload page, check response time and if HTML is served from cache or freshly generated

What to look for: Look for fast initial HTML response times under 100ms indicating cached content; slow times indicate no caching