Revalidation strategies (time-based) in NextJS

Introduction

Revalidation strategies help keep your website data fresh by updating it automatically after a set time. This way, users see recent content without waiting for a full rebuild.

You want your blog posts to update every 10 seconds without rebuilding the whole site.

You have a product page that should refresh data every minute to show latest prices.

You want to cache a page but still update it regularly to keep content fresh.

You want to balance fast page loads with up-to-date information.

Syntax

NextJS

export async function getStaticProps() {
  // fetch data here
  return {
    props: { data },
    revalidate: 10, // seconds
  };
}

The revalidate value is in seconds and tells Next.js how often to update the page.

Next.js will serve the cached page until the revalidation time passes, then update in the background.

Examples

This example updates the page every minute.

NextJS

export async function getStaticProps() {
  return {
    props: { message: 'Hello!' },
    revalidate: 60, // update every 60 seconds
  };
}

This example shows the current time and refreshes it every 5 seconds.

NextJS

export async function getStaticProps() {
  return {
    props: { time: new Date().toISOString() },
    revalidate: 5, // update every 5 seconds
  };
}

Sample Program

This Next.js page shows the time it was generated. It updates automatically every 10 seconds using time-based revalidation.

NextJS

import React from 'react';

export async function getStaticProps() {
  const currentTime = new Date().toISOString();
  return {
    props: { currentTime },
    revalidate: 10, // revalidate every 10 seconds
  };
}

export default function TimePage({ currentTime }) {
  return (
    <main>
      <h1>Current Time</h1>
      <p>The page was generated at:</p>
      <time dateTime={currentTime}>{currentTime}</time>
    </main>
  );
}

Important Notes

Revalidation happens in the background, so users see the old page until the new one is ready.

If you set revalidate to 0 or omit it, the page will not update automatically.

Use time-based revalidation to balance performance and freshness.

Summary

Time-based revalidation updates static pages automatically after a set number of seconds.

This keeps content fresh without rebuilding the whole site manually.

Set revalidate in getStaticProps to control update frequency.

Practice

1. What does setting the revalidate property in getStaticProps do in Next.js?

easy

A. It tells Next.js to update the static page automatically after the specified seconds.

B. It disables static generation and forces server-side rendering.

C. It caches the page forever without any updates.

D. It triggers a client-side fetch to update the page content.

Solution

1. Step 1: Understand revalidate role in getStaticProps

   The revalidate property sets a time interval in seconds for Next.js to regenerate the static page in the background.

2. Step 2: Effect of setting revalidate

   After the specified time, Next.js updates the static page automatically without manual rebuilds or disabling static generation.

3. Final Answer:

   It tells Next.js to update the static page automatically after the specified seconds. -> Option A

4. Quick Check:

   Time-based revalidation = automatic page update [OK]

Hint: Remember: revalidate sets auto-update time in seconds [OK]

Common Mistakes:

• Thinking revalidate disables static generation
• Confusing revalidate with client-side fetching
• Assuming revalidate caches forever

2. Which of the following is the correct way to set a 10-second revalidation in getStaticProps?

easy

A. export async function getStaticProps() { return { props: {}, revalidate: null } }

B. export async function getStaticProps() { return { props: {}, revalidate: '10' } }

C. export async function getStaticProps() { return { props: {}, revalidate: true } }

D. export async function getStaticProps() { return { props: {}, revalidate: 10 } }

Solution

1. Step 1: Check the type of revalidate

   The revalidate value must be a number representing seconds.

2. Step 2: Validate each option's syntax

   export async function getStaticProps() { return { props: {}, revalidate: 10 } } uses a number 10 correctly. export async function getStaticProps() { return { props: {}, revalidate: '10' } } uses a string '10' which is invalid. The other options use boolean and null, which are incorrect types.

3. Final Answer:

   export async function getStaticProps() { return { props: {}, revalidate: 10 } } -> Option D

4. Quick Check:

   revalidate must be a number [OK]

Hint: Use a number for revalidate seconds, not string or boolean [OK]

Common Mistakes:

• Using string instead of number for revalidate
• Setting revalidate to true or null
• Forgetting to return revalidate inside the returned object

3. Given this code snippet in getStaticProps:

export async function getStaticProps() {
  return {
    props: { time: Date.now() },
    revalidate: 5
  }
}

What will happen if you visit the page multiple times within 3 seconds?

medium

A. The page will show the same time value for all visits within 3 seconds.

B. The page will update time on every visit regardless of time.

C. The page will throw an error because revalidate is too short.

D. The page will never update the time value.

Solution

1. Step 1: Understand revalidate timing

   The revalidate: 5 means Next.js regenerates the page at most every 5 seconds.

2. Step 2: Behavior within 3 seconds

   Visiting within 3 seconds means the cached page is served with the same time value because regeneration hasn't happened yet.

3. Final Answer:

   The page will show the same time value for all visits within 3 seconds. -> Option A

4. Quick Check:

   Revalidate interval controls update frequency [OK]

Hint: Page updates only after revalidate seconds pass [OK]

Common Mistakes:

• Expecting page to update on every visit
• Thinking revalidate causes errors if too small
• Assuming page never updates after first build

4. You set revalidate: 0 in getStaticProps. What is the problem with this code?

medium

A. It causes the page to never render.

B. It caches the page forever without updates.

C. It disables static generation and causes a build error.

D. It causes the page to regenerate on every request, similar to server-side rendering.

Solution

1. Step 1: Understand revalidate: 0 meaning

   Setting revalidate to 0 disables Incremental Static Regeneration (ISR). The page is generated at build time and cached forever without background regeneration.

2. Step 2: Effect on page behavior

   This results in no automatic updates, which is the problem if revalidation was intended, behaving like static generation without ISR.

3. Final Answer:

   It caches the page forever without updates. -> Option B

4. Quick Check:

   revalidate 0 = no ISR, cache forever [OK]

Hint: revalidate: 0 caches forever, no updates [OK]

Common Mistakes:

• Thinking revalidate: 0 regenerates on every request
• Believing it causes a build error
• Assuming it prevents the page from rendering

5. You want a page to update its static content every 60 seconds but only if the content has changed. Which Next.js feature combined with revalidate helps achieve this efficiently?

hard

A. Use getServerSideProps instead of getStaticProps.

B. Use revalidate: false to disable updates and manually rebuild.

C. Use revalidate: 60 with Incremental Static Regeneration (ISR) and conditional data fetching.

D. Set revalidate: 0 to regenerate on every request.

Solution

1. Step 1: Understand ISR with revalidate

   Incremental Static Regeneration (ISR) allows pages to update after a set time without full rebuilds.

2. Step 2: Combine with conditional data fetching

   Fetching data conditionally inside getStaticProps ensures updates only when content changes, saving resources.

3. Final Answer:

   Use revalidate: 60 with Incremental Static Regeneration (ISR) and conditional data fetching. -> Option C

4. Quick Check:

   ISR + revalidate = efficient timed updates [OK]

Hint: ISR with revalidate controls timed updates smartly [OK]

Common Mistakes:

• Using getServerSideProps which disables static caching
• Setting revalidate to false which is invalid
• Using revalidate 0 causing regen every request