Cache configuration in Spring Boot - Performance & Optimization

Performance: Cache configuration

HIGH IMPACT

Cache configuration affects how fast data is served by reducing backend calls, improving response time and reducing server load.

Serving frequently requested data efficiently

Spring Boot

@Cacheable("items")
public Item getItem(Long id) {
  return repository.findById(id).orElse(null);
}

Caches results after first call, serving subsequent requests from fast in-memory cache.

📈 Performance GainReduces backend calls by 90%+; lowers response time to under 20 ms.

Serving frequently requested data efficiently

Spring Boot

No caching configured; every request hits the database or backend service directly.

Each request triggers expensive backend calls causing slow response and high server load.

📉 Performance CostBlocks rendering for 100+ ms per request; increases server CPU usage significantly.

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
No cache	N/A	N/A	High backend delay blocks paint	[X] Bad
Cache without limits	N/A	N/A	Possible GC pauses cause paint jank	[!] OK
Proper cache with limits and preload	N/A	N/A	Fast data delivery, smooth paint	[OK] Good

Rendering Pipeline

Cache configuration reduces backend data fetching, speeding up the critical rendering path by serving data faster and reducing layout delays.

→Network

→JavaScript Execution

→Layout

→Paint

⚠️ BottleneckNetwork and backend data fetching delays

Core Web Vital Affected

LCP

Cache configuration affects how fast data is served by reducing backend calls, improving response time and reducing server load.

Optimization Tips

1Always configure cache size limits to prevent memory issues.

2Use @Cacheable annotations to reduce backend calls.

3Preload cache on startup to improve initial response times.

Performance Quiz - 3 Questions

How does enabling cache configuration in Spring Boot affect page load speed?

A Reduces backend calls, speeding up data delivery and improving LCP

B Increases backend calls, slowing down page load

C Has no effect on page load speed

D Blocks rendering until cache is cleared

DevTools: Performance

How to check: Record a performance profile while loading pages; look for long backend calls and blocking times.

What to look for: Short backend call durations and reduced blocking times indicate good cache usage.

Practice

1. What is the primary purpose of using cache configuration in a Spring Boot application?

easy

A. To temporarily store data and speed up application performance

B. To permanently save data to the database

C. To encrypt sensitive data before sending it

D. To manage user authentication and authorization

Solution

1. Step 1: Understand caching concept

   Caching stores data temporarily to avoid repeated processing or fetching.

2. Step 2: Identify caching benefit in Spring Boot

   It speeds up the app by reusing stored data instead of recalculating or fetching again.

3. Final Answer:

   To temporarily store data and speed up application performance -> Option A

4. Quick Check:

   Cache = Temporary storage for speed [OK]

Hint: Cache means temporary storage to speed up apps [OK]

Common Mistakes:

• Confusing cache with permanent database storage
• Thinking cache encrypts data
• Mixing cache with security features

2. Which annotation is used to enable caching support in a Spring Boot application?

easy

A. @EnableCaching

B. @Cacheable

C. @CacheConfig

D. @CachePut

Solution

1. Step 1: Recall Spring Boot caching setup

   To activate caching, Spring Boot requires a special annotation on a configuration class.

2. Step 2: Identify the correct annotation

   @EnableCaching enables the caching mechanism globally in the app.

3. Final Answer:

   @EnableCaching -> Option A

4. Quick Check:

   @EnableCaching activates caching [OK]

Hint: Enable caching with @EnableCaching annotation [OK]

Common Mistakes:

• Using @Cacheable to enable caching (it marks methods, not enable)
• Confusing @CachePut with enabling caching
• Thinking @CacheConfig enables caching globally

3. Given the code below, what will be the output when getUser(1) is called twice?

@Cacheable("users")
public User getUser(int id) {
    System.out.println("Fetching user from DB");
    return new User(id, "Name" + id);
}

medium

A. Fetching user from DB printed twice, two User objects returned

B. No output printed, both calls return null

C. Fetching user from DB printed once, but both calls create new User

D. Fetching user from DB printed once, second call returns cached User

Solution

1. Step 1: Understand @Cacheable behavior

   The first call runs the method and caches the result; subsequent calls return cached data.

2. Step 2: Analyze output for two calls

   "Fetching user from DB" prints only once on first call; second call uses cache, no print.

3. Final Answer:

   Fetching user from DB printed once, second call returns cached User -> Option D

4. Quick Check:

   @Cacheable caches after first call [OK]

Hint: First call runs method, next calls use cache [OK]

Common Mistakes:

• Assuming method runs every time ignoring cache
• Thinking cache returns null if not found
• Confusing @Cacheable with @CachePut behavior

4. Identify the error in this cache configuration snippet:

@Configuration
@EnableCaching
public class CacheConfig {
    @Bean
    public CacheManager cacheManager() {
        return new CacheManager();
    }
}

medium

A. Missing @Cacheable annotation on methods

B. CacheManager is an interface and cannot be instantiated directly

C. Missing @EnableCaching annotation

D. CacheManager bean method should be static

Solution

1. Step 1: Check CacheManager instantiation

   CacheManager is an interface; you cannot create it with new CacheManager().

2. Step 2: Correct way to create CacheManager bean

   You must return a concrete implementation like ConcurrentMapCacheManager.

3. Final Answer:

   CacheManager is an interface and cannot be instantiated directly -> Option B

4. Quick Check:

   CacheManager interface needs implementation [OK]

Hint: CacheManager is interface; use implementation class [OK]

Common Mistakes:

• Trying to instantiate interface directly
• Forgetting to add @EnableCaching
• Thinking @Cacheable is needed on config class

5. You want to configure a cache in Spring Boot that stores user data and expires entries after 10 minutes. Which approach correctly combines cache configuration and expiration?

hard

A. Use @EnableCaching and define a ConcurrentMapCacheManager bean with TTL set to 10 minutes

B. Use @CachePut and manually remove cache entries after 10 minutes

C. Use @EnableCaching and configure a CaffeineCacheManager with expiry policy of 10 minutes

D. Use @Cacheable with a parameter to set expiration time to 10 minutes

Solution

1. Step 1: Understand cache expiration support

   ConcurrentMapCacheManager does not support TTL (time to live) expiration by default.

2. Step 2: Identify cache manager with TTL support

   CaffeineCacheManager supports expiration policies like 10-minute TTL.

3. Step 3: Evaluate options

   @Cacheable does not accept expiration parameters; @CachePut updates cache but does not manage expiration automatically.

4. Final Answer:

   Use @EnableCaching and configure a CaffeineCacheManager with expiry policy of 10 minutes -> Option C

5. Quick Check:

   CaffeineCacheManager supports TTL expiration [OK]

Hint: Use CaffeineCacheManager for TTL expiration [OK]

Common Mistakes:

• Assuming ConcurrentMapCacheManager supports TTL
• Trying to set expiration via @Cacheable annotation
• Using @CachePut to handle expiration manually