Response caching strategies in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the main benefit of using response caching in GraphQL?

Response caching stores the results of GraphQL queries. What is the primary benefit of this?

A It increases the size of the database by storing duplicate data.

B It reduces the number of times the server must process the same query, improving performance.

C It forces clients to always fetch fresh data from the server.

D It disables query batching to improve security.

💡 Hint

Think about how caching helps with repeated requests.

Response caching saves the results of queries so the server can quickly return data without reprocessing the same query multiple times, which improves performance.

❓ query_result

intermediate

Which caching strategy returns cached data only if the query and variables match exactly?

Given these caching strategies, which one returns cached data only when the query and variables are exactly the same?

A Cache by query name only, ignoring variables.

B Cache by response size.

C Cache by query string and variables (strict matching).

D Cache by user session ID only.

💡 Hint

Consider what strict matching means for caching.

Strict matching caches responses only when both the query and variables match exactly, ensuring correct data is returned for each unique request.

📝 Syntax

advanced

Identify the correct GraphQL cache-control directive syntax to set max-age to 60 seconds.

Which of the following cache-control directives correctly sets the max-age to 60 seconds in a GraphQL schema?

A @cacheControl(maxAge: 60)

B @cacheControl(max_age=60)

C @cacheControl(max-age: 60)

D @cacheControl(maxAge=60)

💡 Hint

Look for correct argument naming and syntax in GraphQL directives.

The correct syntax uses camelCase for argument names and colon to assign values in GraphQL directives.

❓ optimization

advanced

Which approach best optimizes caching for frequently changing user-specific data?

You have user-specific data that changes often. Which caching strategy optimizes performance without serving stale data?

A Use short max-age with cache key including user ID and invalidate cache on updates.

B Use long max-age ignoring user ID in cache key.

C Disable caching completely for user-specific data.

D Cache only the query name without variables.

💡 Hint

Think about balancing freshness and performance for user data.

Short max-age with user-specific cache keys and invalidation ensures fresh data while still benefiting from caching.

🔧 Debug

expert

Why does this GraphQL response caching setup cause stale data to be served?

Consider a GraphQL server that caches responses globally without considering authentication tokens. What is the likely problem?

A The cache key includes authentication tokens, causing cache misses.

B The server crashes due to missing authentication headers.

C Caching is disabled automatically for authenticated queries.

D Cached responses are shared across users, causing one user to see another's data.

💡 Hint

Think about what happens if cache keys do not differentiate users.

If cache keys do not include user authentication info, cached data can be served to the wrong user, causing stale or incorrect data exposure.

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