Response caching strategies in GraphQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is response caching in GraphQL?

Response caching stores the results of GraphQL queries so that repeated requests can be served faster without re-executing the query.

beginner

Name a common strategy for caching GraphQL responses.

One common strategy is query-based caching, where the exact query string and variables are used as a key to store and retrieve cached results.

intermediate

What is the difference between client-side and server-side caching in GraphQL?

Client-side caching stores responses in the user's browser or app to reduce network calls. Server-side caching stores responses on the server to reduce database or resolver load.

intermediate

How does cache invalidation affect response caching?

Cache invalidation removes or updates cached data when the underlying data changes, ensuring clients get fresh and accurate responses.

beginner

What role do Cache-Control headers play in GraphQL response caching?

Cache-Control headers tell clients and proxies how long to keep a cached response and whether it can be reused, helping control caching behavior.

Which of the following is a key used in query-based caching for GraphQL?

A The exact query string and variables

B Only the query name

C The server IP address

D The client's user agent

Query-based caching uses the full query string and variables as the key to ensure the cached response matches the request exactly.

What does cache invalidation ensure in response caching?

A That cached data is always kept forever

B That cached data is updated or removed when underlying data changes

C That cache size is unlimited

D That only client-side caching is used

Cache invalidation updates or removes cached data to keep responses accurate when the original data changes.

Where is client-side caching stored?

A In the database

B On the server

C In the user's browser or app

D In the network router

Client-side caching stores data locally in the user's browser or app to reduce network requests.

What does the Cache-Control header NOT control?

A The exact data format of the response

B Whether a response can be reused

C How long to keep a cached response

D Caching behavior for clients and proxies

Cache-Control headers control caching behavior but do not specify the data format of the response.

Which caching strategy reduces load on the database or resolvers?

A Client-side caching

B DNS caching

C Browser caching

D Server-side caching

Server-side caching stores responses on the server to reduce the need to run expensive database queries or resolver functions.

Explain how response caching improves performance in GraphQL APIs.

Think about what happens when the same query is asked multiple times.

Describe the difference between client-side and server-side caching in GraphQL.

Consider where the cached data lives and what it helps reduce.

Practice

1. What is the main purpose of response caching in GraphQL?

easy

A. To store query results and speed up repeated requests

B. To encrypt data sent between client and server

C. To validate user permissions for queries

D. To log all queries for debugging

Solution

1. Step 1: Understand response caching concept

   Response caching saves the answers of queries so that if the same query is asked again, the server can quickly return the saved answer instead of recalculating it.

2. Step 2: Identify the main benefit

   This speeds up repeated requests and reduces server load.

3. Final Answer:

   To store query results and speed up repeated requests -> Option A

4. Quick Check:

   Response caching = store and speed up [OK]

Hint: Caching saves answers to reuse later, speeding up requests [OK]

Common Mistakes:

• Confusing caching with encryption
• Thinking caching controls permissions
• Believing caching logs queries

2. Which of the following is the correct way to set a cache duration using the @cacheControl directive in GraphQL SDL?

easy

A. @cacheControl(duration: 60)

B. @cacheControl(maxAge: 60)

C. @cacheControl(cacheTime: 60)

D. @cacheControl(time: 60)

Solution

1. Step 1: Recall the correct directive syntax

   The @cacheControl directive uses the argument maxAge to specify cache duration in seconds.

2. Step 2: Match the correct argument name

   Only maxAge is valid; other argument names like duration, cacheTime, or time are incorrect.

3. Final Answer:

   @cacheControl(maxAge: 60) -> Option B

4. Quick Check:

   @cacheControl uses maxAge [OK]

Hint: Use maxAge to set cache seconds in @cacheControl [OK]

Common Mistakes:

• Using wrong argument names like duration or time
• Omitting the argument name
• Using invalid directive syntax

3. Given this GraphQL query with caching set to @cacheControl(maxAge: 120), what happens if the same query is requested twice within 2 minutes?

medium

A. The server returns the cached response on the second request

B. The server returns an error on the second request

C. The server recalculates the response both times

D. The cache is ignored and data is fetched fresh every time

Solution

1. Step 1: Understand maxAge meaning

   The maxAge: 120 means the response is cached for 120 seconds (2 minutes).

2. Step 2: Analyze repeated request timing

   If the second request happens within 2 minutes, the cached response is still valid and returned immediately.

3. Final Answer:

   The server returns the cached response on the second request -> Option A

4. Quick Check:

   maxAge 120 means cache valid 2 minutes [OK]

Hint: Within maxAge, cached response is reused [OK]

Common Mistakes:

• Thinking cache expires immediately
• Assuming server errors on repeated queries
• Believing cache is ignored always

4. You set @cacheControl(maxAge: -10) on a field. What is the likely problem?

medium

A. Negative maxAge causes a syntax error

B. Negative maxAge disables caching for that field

C. Negative maxAge is treated as zero, caching forever

D. Negative maxAge causes cache to expire immediately

Solution

1. Step 1: Understand maxAge value meaning

   maxAge defines how long the response is cached in seconds. Negative values are invalid for duration.

2. Step 2: Interpret negative maxAge effect

   Negative maxAge is treated as cache expired immediately, so no caching occurs effectively.

3. Final Answer:

   Negative maxAge causes cache to expire immediately -> Option D

4. Quick Check:

   Negative maxAge means cache expires instantly [OK]

Hint: Negative maxAge means cache expires right away [OK]

Common Mistakes:

• Expecting syntax error from negative value
• Thinking negative disables caching explicitly
• Assuming negative means cache forever

5. You want to cache a GraphQL query response for a user profile that updates frequently but not every second. Which caching strategy is best?

hard

A. Set @cacheControl(maxAge: 5) to cache for 5 seconds

B. Set @cacheControl(maxAge: 3600) to cache for 1 hour

C. Set @cacheControl(maxAge: 300) to cache for 5 minutes

D. Do not use caching to always get fresh data

Solution

1. Step 1: Consider data freshness needs

   User profiles update frequently but not every second, so caching too long risks stale data.

2. Step 2: Choose a balanced cache duration

   5 seconds is too short to gain caching benefits; 1 hour is too long risking stale data. 5 minutes (300 seconds) balances freshness and performance.

3. Final Answer:

   Set @cacheControl(maxAge: 300) to cache for 5 minutes -> Option C

4. Quick Check:

   Moderate maxAge balances freshness and speed [OK]

Hint: Pick cache time balancing freshness and speed [OK]

Common Mistakes:

• Choosing too short cache time losing benefits
• Choosing too long cache time causing stale data
• Avoiding caching when moderate caching helps