Revalidation strategies (time-based) in NextJS - Mini Project: Build & Apply

Implementing Time-Based Revalidation in Next.js

📖 Scenario: You are building a simple blog homepage using Next.js. The blog posts data is fetched from a static source but you want the page to update automatically every 10 seconds to show any new posts without needing a full redeploy.

🎯 Goal: Build a Next.js page that fetches blog posts data and uses time-based revalidation to update the page every 10 seconds.

📋 What You'll Learn

Create a static array of blog posts with exact titles and ids

Add a revalidation time variable set to 10 seconds

Use getStaticProps to fetch the posts and set the revalidation time

Create a functional React component that displays the blog post titles

💡 Why This Matters

🌍 Real World

Time-based revalidation is useful for blogs, news sites, or any content that updates regularly but does not need real-time updates. It balances performance and freshness.

💼 Career

Understanding Next.js data fetching and revalidation is important for frontend developers working with modern React frameworks to build fast, SEO-friendly websites.

1

Create the blog posts data array

Create a constant array called posts with these exact objects: { id: 1, title: 'Hello Next.js' }, { id: 2, title: 'Learning Revalidation' }, and { id: 3, title: 'Static Props in Next.js' }.

NextJS

// Create the posts array with the specified objects
// Your code here

Hint

Use const posts = [ ... ] with the exact objects inside.

2

Add the revalidation time variable

Create a constant called revalidateTime and set it to 10 to represent 10 seconds.

NextJS

const posts = [
  { id: 1, title: 'Hello Next.js' },
  { id: 2, title: 'Learning Revalidation' },
  { id: 3, title: 'Static Props in Next.js' }
];

// Create the revalidateTime constant and set it to 10
// Your code here

Hint

Use const revalidateTime = 10; to set the revalidation time.

3

Implement getStaticProps with revalidation

Write an async function called getStaticProps that returns an object with props containing the posts array and a revalidate property set to revalidateTime.

NextJS

const posts = [
  { id: 1, title: 'Hello Next.js' },
  { id: 2, title: 'Learning Revalidation' },
  { id: 3, title: 'Static Props in Next.js' }
];

const revalidateTime = 10;

// Write the getStaticProps function below
// Your code here

Hint

Use export async function getStaticProps() { return { props: { posts }, revalidate: revalidateTime } }.

4

Create the React component to display posts

Create a default exported functional component called HomePage that accepts posts as a prop and returns a <main> element containing an unordered list. Each list item should display the post's title and have a key set to the post's id.

NextJS

const posts = [
  { id: 1, title: 'Hello Next.js' },
  { id: 2, title: 'Learning Revalidation' },
  { id: 3, title: 'Static Props in Next.js' }
];

const revalidateTime = 10;

export async function getStaticProps() {
  return {
    props: { posts },
    revalidate: revalidateTime
  };
}

// Create the HomePage component below
// Your code here

Hint

Use export default function HomePage({ posts }) { return ( <main><ul>{posts.map(post => <li key={post.id}>{post.title}</li>)}</ul></main> ) }.

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