Why rendering strategy matters in NextJS - Performance Evidence

Performance: Why rendering strategy matters

HIGH IMPACT

Rendering strategy affects how fast the main content appears and how quickly users can interact with the page.

Rendering a page with dynamic data

NextJS

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

export default function Page({ data }) {
  return <div>{data.title}</div>;
}

Pre-fetching data during build or server-side rendering allows the page to render immediately with content.

📈 Performance GainReduces LCP by loading content faster and avoids blocking rendering.

Rendering a page with dynamic data

NextJS

export default async function Page() {
  const data = await fetch('https://api.example.com/data').then(res => res.json());
  return <div>{data.title}</div>;
}

Fetching data directly in the component without server-side rendering delays content display and blocks rendering.

📉 Performance CostBlocks rendering until data fetch completes, increasing LCP by 1-3 seconds depending on network.

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Client-side data fetching	Many (delayed DOM update)	Multiple (due to late content injection)	High (delayed paint)	[X] Bad
Server-side or static rendering	Few (immediate DOM ready)	Single (initial layout)	Low (fast paint)	[OK] Good

Rendering Pipeline

Rendering strategy determines when and where data is fetched and HTML is generated, affecting the browser's ability to paint content quickly.

→HTML Generation

→Style Calculation

→Layout

→Paint

⚠️ BottleneckHTML Generation when data fetching blocks rendering

Core Web Vital Affected

LCP, INP

Rendering strategy affects how fast the main content appears and how quickly users can interact with the page.

Optimization Tips

1Pre-render pages on the server or at build time to speed up initial content display.

2Avoid fetching data on the client during initial load to reduce blocking and improve responsiveness.

3Choose rendering strategies based on content freshness needs to balance performance and data accuracy.

Performance Quiz - 3 Questions

Which rendering strategy generally improves Largest Contentful Paint (LCP) the most?

A Client-side rendering with data fetching after load

B Server-side rendering or static generation

C Rendering only on user interaction

D Using heavy animations on load

DevTools: Performance

How to check: Record a page load and look for the Largest Contentful Paint event timing and scripting blocking time.

What to look for: Long gaps before LCP or heavy scripting blocking indicate poor rendering strategy.

Practice

1. In Next.js, why does choosing the right rendering strategy matter for your website?

easy

A. It decides which fonts are used on the page.

B. It changes the color scheme of the website automatically.

C. It controls the size of images on the page.

D. It affects how fast the page loads and how fresh the content is.

Solution

1. Step 1: Understand rendering strategy impact

   Rendering strategy determines when and how page content is created and delivered to users.

2. Step 2: Connect rendering to performance and freshness

   Choosing the right strategy affects page load speed and how up-to-date the content appears, which is important for user experience and SEO.

3. Final Answer:

   It affects how fast the page loads and how fresh the content is. -> Option D

4. Quick Check:

   Rendering strategy = speed and freshness [OK]

Hint: Rendering strategy controls speed and content freshness [OK]

Common Mistakes:

• Thinking rendering changes colors or fonts
• Confusing rendering with styling or image size
• Assuming rendering affects only visuals, not performance

2. Which Next.js page export correctly sets a page to use Static Site Generation (SSG)?

easy

A. export default function Page() { return Hello }

B. export const getServerSideProps = async () => { return { props: {} } }

C. export const getStaticProps = async () => { return { props: {} } }

D. export const getInitialProps = async () => { return { props: {} } }

Solution

1. Step 1: Identify SSG method in Next.js

   Static Site Generation uses getStaticProps to fetch data at build time.

2. Step 2: Match export to SSG

   Only getStaticProps triggers SSG; others are for server-side or legacy methods.

3. Final Answer:

   export const getStaticProps = async () => { return { props: {} } } -> Option C

4. Quick Check:

   SSG = getStaticProps [OK]

Hint: SSG uses getStaticProps export [OK]

Common Mistakes:

• Confusing getServerSideProps with SSG
• Using getInitialProps which is legacy
• Not exporting any data fetching function

3. Given this Next.js page code, what will the user see when visiting the page?

export async function getServerSideProps() {
  return { props: { time: new Date().toISOString() } };
}

export default function Page({ time }) {
  return 
Current time: {time}
;
}

medium

A. The current server time updated on every request.

B. The time when the site was built, never changes.

C. An error because getServerSideProps cannot return props.

D. A blank page because time is undefined.

Solution

1. Step 1: Understand getServerSideProps behavior

   This function runs on every request, fetching fresh data each time.

2. Step 2: Analyze returned props usage

   The page receives the current server time as a prop and displays it inside the div.

3. Final Answer:

   The current server time updated on every request. -> Option A

4. Quick Check:

   getServerSideProps = fresh data each request [OK]

Hint: getServerSideProps runs every request, shows fresh data [OK]

Common Mistakes:

• Thinking it shows build time (that's SSG)
• Assuming getServerSideProps causes errors
• Believing props are undefined without checking code

4. This Next.js page uses Static Site Generation but the data is not updating after deployment. What is the likely fix?

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

export default function Page({ data }) {
  return 
{data.message}
;
}

medium

A. Add revalidate property to enable Incremental Static Regeneration.

B. Change getStaticProps to getServerSideProps to fetch on every request.

C. Remove the fetch call to avoid stale data.

D. Wrap the component in React.memo to force updates.

Solution

1. Step 1: Identify SSG data freshness issue

   Static Site Generation builds pages once at build time, so data stays static unless re-built.

2. Step 2: Use revalidate for periodic updates

   Adding revalidate enables Incremental Static Regeneration, refreshing data after set seconds.

3. Final Answer:

   Add revalidate property to enable Incremental Static Regeneration. -> Option A

4. Quick Check:

   SSG + revalidate = fresh static pages [OK]

Hint: Use revalidate in getStaticProps for fresh static data [OK]

Common Mistakes:

• Switching to getServerSideProps unnecessarily
• Removing fetch which breaks data loading
• Using React.memo which doesn't affect data fetching

5. You want a Next.js page that shows user profile data that updates every 10 seconds but also loads fast initially. Which rendering strategy best fits this need?

hard

A. Use Server-side Rendering with getServerSideProps to fetch data on every request.

B. Use Static Site Generation with revalidate: 10 to update every 10 seconds.

C. Use Client-side Rendering only with useEffect to fetch data after page loads.

D. Use Static Site Generation without revalidate for fastest load.

Solution

1. Step 1: Understand the need for fast initial load and frequent updates

   Static Site Generation gives fast load by pre-building pages; revalidate allows periodic updates.

2. Step 2: Compare options for update frequency and speed

   Using revalidate: 10 updates the page every 10 seconds without slowing initial load, unlike server-side rendering which runs every request.

3. Final Answer:

   Use Static Site Generation with revalidate: 10 to update every 10 seconds. -> Option B

4. Quick Check:

   SSG + revalidate = fast + fresh [OK]

Hint: SSG with revalidate balances speed and freshness [OK]

Common Mistakes:

• Choosing server-side rendering which slows initial load
• Using client-side fetching which delays content display
• Ignoring revalidate option for periodic updates