Fetch caching behavior in NextJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does fetch caching mean in Next.js?

Fetch caching means storing the results of a fetch request so that future requests can use the stored data instead of fetching again, making the app faster and saving resources.

intermediate

How does Next.js decide when to use cached fetch data?

Next.js uses cache based on the fetch options like 'cache: "force-cache"' to reuse data, or 'cache: "no-store"' to always fetch fresh data. It also respects HTTP cache headers.

intermediate

What is the default caching behavior of fetch in Next.js 13+?

By default, fetch in Next.js 13+ caches data on the server for the duration of the request lifecycle, improving performance by avoiding repeated fetches during server rendering.

beginner

How can you disable fetch caching in Next.js?

You can disable fetch caching by setting the fetch option 'cache' to 'no-store'. This forces fetch to get fresh data every time without using cache.

intermediate

Why is fetch caching important in server components of Next.js?

Fetch caching helps server components avoid repeated data fetching during rendering, which speeds up page loads and reduces server load, making the app more efficient.

In Next.js, which fetch option forces fresh data every time?

A cache: "default"

B cache: "force-cache"

C cache: "immutable"

D cache: "no-store"

Setting cache to "no-store" disables caching and fetches fresh data on every request.

What is the default fetch caching behavior in Next.js 13+ server components?

A Cache data for the request lifecycle

B Always fetch fresh data

C Cache data indefinitely

D No caching at all

By default, fetch caches data during the server request lifecycle to improve performance.

Which HTTP headers can influence fetch caching behavior in Next.js?

A Cache-Control and ETag

B Content-Type and Accept

C Authorization and Cookie

D User-Agent and Referer

Cache-Control and ETag headers help control caching behavior of fetch requests.

Why should you use fetch caching in server components?

A To make client components slower

B To reduce server load and speed up rendering

C To disable data fetching

D To increase network requests

Caching reduces repeated fetches, lowering server load and speeding up page rendering.

How do you tell fetch to reuse cached data in Next.js?

A cache: "reload"

B cache: "no-store"

C cache: "force-cache"

D cache: "no-cache"

"force-cache" tells fetch to reuse cached data if available.

Explain how fetch caching works in Next.js and why it matters for server components.

Think about how caching avoids repeated data fetching.

Describe how you can control fetch caching behavior in Next.js with examples.

Consider fetch options and HTTP headers.

Practice

1. In Next.js, what does setting cache: "force-cache" in a fetch call do?

easy

A. It returns cached data if available, otherwise fetches from the network.

B. It always fetches fresh data from the network, ignoring cache.

C. It disables caching completely for the fetch request.

D. It caches the response only for the current session.

Solution

1. Step 1: Understand the cache option "force-cache"

   This option tells Next.js to use cached data if it exists, avoiding a network request.

2. Step 2: Behavior when cache is missing

   If no cached data is found, it fetches fresh data and caches it for future use.

3. Final Answer:

   It returns cached data if available, otherwise fetches from the network. -> Option A

4. Quick Check:

   force-cache = use cache first [OK]

Hint: force-cache means use cache if present, else fetch fresh [OK]

Common Mistakes:

• Confusing force-cache with no-store which disables cache
• Thinking force-cache always fetches fresh data
• Assuming force-cache caches only for session

2. Which of the following is the correct syntax to fetch data with no caching in Next.js?

easy

A. fetch(url, { cache: "force-cache" })

B. fetch(url, { cache: "default" })

C. fetch(url, { cache: "reload" })

D. fetch(url, { cache: "no-store" })

Solution

1. Step 1: Identify the option for no caching

   The no-store cache mode disables caching and always fetches fresh data.

2. Step 2: Verify syntax correctness

   The syntax fetch(url, { cache: "no-store" }) is valid and correctly disables cache.

3. Final Answer:

   fetch(url, { cache: "no-store" }) -> Option D

4. Quick Check:

   no-store disables cache [OK]

Hint: Use cache: "no-store" to disable caching [OK]

Common Mistakes:

• Using "reload" which is not a valid cache option in Next.js fetch
• Confusing "force-cache" with no caching
• Omitting the cache option entirely

3. What will be the behavior of this Next.js fetch call?

await fetch('/api/data', { cache: 'no-cache' })

medium

A. Returns cached data if available, but revalidates in background.

B. Always fetches fresh data and updates the cache.

C. Ignores cache and never stores the response.

D. Fetches from cache only, never from network.

Solution

1. Step 1: Understand the 'no-cache' mode

   This mode returns cached data if available but triggers a background fetch to update the cache.

2. Step 2: Confirm behavior in Next.js fetch

   Next.js uses this to balance speed and freshness by serving cache immediately and updating it asynchronously.

3. Final Answer:

   Returns cached data if available, but revalidates in background. -> Option A

4. Quick Check:

   no-cache = cache then revalidate [OK]

Hint: no-cache serves cache then refreshes in background [OK]

Common Mistakes:

• Thinking no-cache disables cache completely
• Assuming no-cache never uses cached data
• Confusing no-cache with no-store

4. You wrote this fetch call in Next.js:

fetch('/api/data', { cache: 'reload' })

But it throws an error. What is the problem?

medium

A. You must use async/await with fetch.

B. You forgot to add method: 'GET' in options.

C. "reload" is not a valid cache option in Next.js fetch.

D. The URL must be absolute, not relative.

Solution

1. Step 1: Check valid cache options in Next.js

   Next.js fetch supports "force-cache", "no-store", "no-cache", and "default" but not "reload".

2. Step 2: Identify error cause

   Using "reload" causes a syntax or runtime error because it's unsupported.

3. Final Answer:

   "reload" is not a valid cache option in Next.js fetch. -> Option C

4. Quick Check:

   Invalid cache option = error [OK]

Hint: Check cache option spelling and validity [OK]

Common Mistakes:

• Assuming reload is valid from browser fetch API
• Ignoring error messages about invalid options
• Thinking method or URL causes this error

5. You want to fetch user data in Next.js and ensure it is always fresh but also want to avoid unnecessary network requests if the data was fetched less than 10 seconds ago. Which caching strategy should you use?

hard

A. Use cache: 'no-store' and implement a custom timer to refetch every 10 seconds.

B. Use cache: 'no-cache' with next: { revalidate: 10 } option.

C. Use cache: 'force-cache' with next: { revalidate: 10 } option.

D. Use cache: 'default' without revalidation.

Solution

1. Step 1: Understand requirement for freshness and caching

   You want fresh data but avoid fetching more than once every 10 seconds.

2. Step 2: Analyze caching options

   cache: 'no-cache' serves cached data but revalidates in background; next: { revalidate: 10 } tells Next.js to re-fetch after 10 seconds.

3. Step 3: Compare with other options

   no-store disables cache completely, forcing fetch every time; force-cache caches indefinitely; default has no revalidation control.

4. Final Answer:

   Use cache: 'no-cache' with next: { revalidate: 10 } option. -> Option B

5. Quick Check:

   no-cache + revalidate = fresh every 10s [OK]

Hint: Combine no-cache with revalidate for timed freshness [OK]

Common Mistakes:

• Using no-store causes always fresh but no caching
• Using force-cache ignores revalidate timing
• Forgetting to add revalidate option