Revalidation patterns in NextJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a page to revalidate every 60 seconds.

NextJS

export const revalidate = [1];

Drag options to blanks, or click blank then click option'

A60

B'60'

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number for revalidate.

Setting revalidate to true or false instead of a number.

The revalidate export expects a number representing seconds for ISR (Incremental Static Regeneration).

2fill in blank

medium

Complete the code to fetch data with revalidation set to 10 seconds inside a Next.js Server Component.

NextJS

const data = await fetch('https://api.example.com/data', { cache: '[1]' });

Drag options to blanks, or click blank then click option'

A'no-store'

B'default'

C'force-cache'

D'force-cache', revalidate: 10

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'no-store' disables caching and revalidation.

Trying to pass revalidate inside fetch options directly.

Using 'force-cache' cache mode allows Next.js to apply the revalidate setting for ISR.

3fill in blank

hard

Fix the error in the fetch call to enable revalidation every 30 seconds.

NextJS

const res = await fetch('/api/data', { cache: '[1]' });

Drag options to blanks, or click blank then click option'

A'default'

B'no-store'

C'no-cache'

D'force-cache'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'no-store' disables caching and revalidation.

Using invalid options like 'default' or 'no-cache'.

The 'force-cache' cache mode allows Next.js to use the revalidate time set in the page or layout.

4fill in blank

hard

Fill both blanks to create a fetch call that caches data and revalidates every 15 seconds.

NextJS

const data = await fetch('/api/data', { cache: '[1]', next: { revalidate: [2] } });

Drag options to blanks, or click blank then click option'

A'force-cache'

B'no-store'

C15

D30

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'no-store' disables caching.

Setting revalidate to a string instead of a number.

Using 'force-cache' with next.revalidate set to 15 enables caching with revalidation every 15 seconds.

5fill in blank

hard

Fill all three blanks to create a Next.js page that revalidates every 20 seconds and fetches data with caching.

NextJS

export const revalidate = [1];

export default async function Page() {
  const data = await fetch('/api/info', { cache: '[2]', next: { revalidate: [3] } });
  return <pre>{JSON.stringify(data)}</pre>;
}

Drag options to blanks, or click blank then click option'

A20

B'force-cache'

D'no-store'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'no-store' disables caching and revalidation.

Mismatching revalidate times between export and fetch.

The page sets revalidate to 20 seconds. The fetch uses 'force-cache' with next.revalidate also set to 20 to enable ISR caching.

Practice

1. What does the revalidate export in Next.js control?

easy

A. How often a cached page updates after initial generation

B. The maximum number of pages to cache

C. The delay before a page is first generated

D. The priority of server-side rendering

Solution

1. Step 1: Understand the role of revalidate

   The revalidate export sets the time in seconds for Next.js to update a cached page after it was first generated.

2. Step 2: Compare options with this behavior

   Only How often a cached page updates after initial generation correctly describes this update frequency control. Other options describe unrelated concepts.

3. Final Answer:

   How often a cached page updates after initial generation -> Option A

4. Quick Check:

   Revalidate controls update frequency = D [OK]

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

Common Mistakes:

• Confusing revalidate with cache size
• Thinking revalidate delays first page generation
• Mixing revalidate with rendering priority

2. Which of the following is the correct syntax to set a page to revalidate every 60 seconds in Next.js?

easy

A. export revalidate = 60;

B. export const revalidate = 60;

C. const revalidate = 60 export;

D. export const revalidate(60);

Solution

1. Step 1: Recall correct export syntax in Next.js

   To export a constant, the syntax is export const name = value;.

2. Step 2: Match this with revalidate usage

   export const revalidate = 60; matches this pattern exactly. Other options have syntax errors or misplaced keywords.

3. Final Answer:

   export const revalidate = 60; -> Option B

4. Quick Check:

   Correct export syntax = A [OK]

Hint: Use 'export const' to export revalidate value [OK]

Common Mistakes:

• Omitting 'const' keyword
• Using parentheses incorrectly
• Placing export keyword after variable

3. Given this Next.js page code snippet:

export const revalidate = 10;

export default function Page() {
  return <div>Time: {Date.now()}</div>;
}

What will happen if you visit this page multiple times within 10 seconds?

medium

A. The page updates the timestamp on every visit immediately

B. The page never updates after the first visit

C. The page throws an error because Date.now() is not allowed

D. The page shows the same timestamp for 10 seconds before updating

Solution

1. Step 1: Understand revalidate timing effect

   With revalidate = 10, Next.js caches the page and only regenerates it after 10 seconds.

2. Step 2: Predict page behavior on multiple visits

   Within 10 seconds, the cached page is served, so the timestamp stays the same. After 10 seconds, it updates.

3. Final Answer:

   The page shows the same timestamp for 10 seconds before updating -> Option D

4. Quick Check:

   Revalidate caches page for 10 seconds = B [OK]

Hint: Revalidate delays page update by set seconds [OK]

Common Mistakes:

• Assuming Date.now() updates on every visit
• Thinking revalidate disables page updates
• Confusing revalidate with client-side rendering

4. You wrote this code in a Next.js page:

export const revalidate = '30';

export default function Page() {
  return <div>Hello</div>;
}

What is the problem with this code?

medium

A. revalidate must be a number, not a string

B. Page component must be async to use revalidate

C. You cannot export revalidate in a page component

D. The return statement is missing parentheses

Solution

1. Step 1: Check the type of revalidate value

   The revalidate export expects a number representing seconds, not a string.

2. Step 2: Identify the error caused by wrong type

   Using a string will cause Next.js to ignore or error on revalidation timing.

3. Final Answer:

   revalidate must be a number, not a string -> Option A

4. Quick Check:

   revalidate requires number type = A [OK]

Hint: Use number, not quotes, for revalidate seconds [OK]

Common Mistakes:

• Using quotes around the number
• Thinking revalidate needs async function
• Misunderstanding export rules

5. You want a Next.js page to show fresh data but also improve performance by caching for 5 minutes. Which revalidation pattern should you use?

export const revalidate = ?;

Choose the best value and explain why.

hard

A. 60, to update every minute for fresher data

B. 0, to disable caching and always fetch fresh data

C. 300, because 300 seconds equals 5 minutes, balancing freshness and caching

D. Infinity, to cache forever and never update

Solution

1. Step 1: Convert 5 minutes to seconds

   5 minutes equals 300 seconds, so revalidate should be set to 300.

2. Step 2: Understand caching vs freshness tradeoff

   Setting revalidate to 300 caches the page for 5 minutes, improving performance but still updating regularly.

3. Step 3: Evaluate other options

   0 disables caching (no performance gain), 60 updates too often, Infinity never updates (stale data).

4. Final Answer:

   300, because 300 seconds equals 5 minutes, balancing freshness and caching -> Option C

5. Quick Check:

   5 minutes = 300 seconds revalidate [OK]

Hint: Set revalidate to seconds matching desired cache time [OK]

Common Mistakes:

• Using 0 thinking it improves performance
• Choosing too short or too long revalidate values
• Confusing minutes with seconds