Caching - Spring Boot Multi-Layer Approach

Caching is one of the most effective optimization techniques that dramatically improves system performance. By temporarily storing data in fast-accessible locations, it minimizes expensive computation and I/O operations. Spring Boot provides comprehensive support for multi-layered caching strategies.

Quick Decision

Situation	Use Cache	Watch Out
Data is read often and changes rarely	Yes	TTL and invalidation must be clear
Computation is expensive	Yes	Cache key must be designed correctly
Data varies by authorization	Be careful	Cross-user leakage risk
Strong correctness after write	Limited	Stale reads may be unacceptable

Production Checklist

Problem: Which expensive operation does the cache reduce?
Solution: Are key, TTL, invalidation, warmup, and fallback behavior clear?
Trade-off: Latency drops; inconsistency, memory, and operational cost are added.
Failure mode: Cache stampede, hot keys, stale data, eviction storms, and Redis outages should be handled.
Measurement: Track hit ratio, miss latency, eviction count, memory usage, and backend load.
Security/cost: Tenant/user separation is required when caching authorized data; large caches create memory cost.

Cache Architecture Overview

Cache Patterns

Cache Pattern Descriptions

Cache-Aside (Lazy Loading)
- Application manually manages the cache
- Automatic data loading on cache miss
- Enables selective caching
Write-Through
- Synchronous write to both cache and database
- Guarantees data consistency
- Requires two operations for each write
Write-Behind (Write-Back)
- Immediate write to cache, asynchronous write to database
- Provides high performance
- Risk of data loss

Distributed Cache Architecture

Application-Level Caching

Spring Cache Abstraction

Spring Cache Abstraction enables managing caching operations through declarative annotations. This approach supports clean code principles by separating caching concerns from business logic.

Key Features:

@Cacheable: Caches method results
@CacheEvict: Removes data from cache
@CachePut: Updates cache on every call
@Caching: Groups multiple cache annotations
Conditional caching: Enables conditional caching capabilities

Cache Provider Comparison:

Redis: Ideal for distributed caching, persistence support
Hazelcast: In-memory data grid, clustering capabilities
Caffeine: High-performance local cache, advanced version of Guava
EhCache: Both local and distributed cache support

Basic Cache Configuration

java

@Configuration
@EnableCaching
public class CacheConfig {
    
    @Bean
    public CacheManager cacheManager() {
        RedisCacheManager.Builder builder = RedisCacheManager
            .RedisCacheManagerBuilder
            .fromConnectionFactory(redisConnectionFactory())
            .cacheDefaults(cacheConfiguration());
        
        return builder.build();
    }
    
    @Bean
    public RedisCacheConfiguration cacheConfiguration() {
        return RedisCacheConfiguration.defaultCacheConfig()
            .entryTtl(Duration.ofMinutes(10))
            .serializeKeysWith(RedisSerializationContext.SerializationPair
                .fromSerializer(new StringRedisSerializer()))
            .serializeValuesWith(RedisSerializationContext.SerializationPair
                .fromSerializer(new GenericJackson2JsonRedisSerializer()));
    }
}

Cache Annotations

java

@Service
public class UserService {
    
    @Cacheable(value = "users", key = "#userId")
    public User getUserById(Long userId) {
        log.info("Fetching user from database: {}", userId);
        return userRepository.findById(userId).orElse(null);
    }
    
    @CachePut(value = "users", key = "#user.id")
    public User updateUser(User user) {
        User updatedUser = userRepository.save(user);
        log.info("User updated and cached: {}", updatedUser.getId());
        return updatedUser;
    }
    
    @CacheEvict(value = "users", key = "#userId")
    public void deleteUser(Long userId) {
        userRepository.deleteById(userId);
        log.info("User deleted and evicted from cache: {}", userId);
    }
    
    @CacheEvict(value = "users", allEntries = true)
    public void clearAllUsers() {
        log.info("All users evicted from cache");
    }
}

Redis Distributed Caching

Redis Configuration

java

@Configuration
public class RedisConfig {
    
    @Bean
    public LettuceConnectionFactory redisConnectionFactory() {
        RedisStandaloneConfiguration config = new RedisStandaloneConfiguration();
        config.setHostName("localhost");
        config.setPort(6379);
        config.setPassword("password");
        
        LettuceClientConfiguration clientConfig = LettuceClientConfiguration.builder()
            .commandTimeout(Duration.ofSeconds(5))
            .poolConfig(connectionPoolConfig())
            .build();
            
        return new LettuceConnectionFactory(config, clientConfig);
    }
    
    @Bean
    public RedisTemplate<String, Object> redisTemplate() {
        RedisTemplate<String, Object> template = new RedisTemplate<>();
        template.setConnectionFactory(redisConnectionFactory());
        
        // JSON serialization
        GenericJackson2JsonRedisSerializer serializer = new GenericJackson2JsonRedisSerializer();
        template.setKeySerializer(new StringRedisSerializer());
        template.setValueSerializer(serializer);
        template.setHashKeySerializer(new StringRedisSerializer());
        template.setHashValueSerializer(serializer);
        
        return template;
    }
    
    private GenericObjectPoolConfig<?> connectionPoolConfig() {
        GenericObjectPoolConfig<?> config = new GenericObjectPoolConfig<>();
        config.setMaxTotal(20);
        config.setMaxIdle(10);
        config.setMinIdle(5);
        return config;
    }
}

Manual Cache Operations

java

@Service
public class CacheService {
    
    @Autowired
    private RedisTemplate<String, Object> redisTemplate;
    
    public void cacheObject(String key, Object value, Duration ttl) {
        redisTemplate.opsForValue().set(key, value, ttl);
    }
    
    public <T> T getCachedObject(String key, Class<T> type) {
        Object cached = redisTemplate.opsForValue().get(key);
        return type.cast(cached);
    }
    
    public void evictFromCache(String key) {
        redisTemplate.delete(key);
    }
    
    public void cacheList(String key, List<Object> list, Duration ttl) {
        redisTemplate.opsForList().rightPushAll(key, list.toArray());
        redisTemplate.expire(key, ttl);
    }
    
    public Set<Object> getCachedSet(String key) {
        return redisTemplate.opsForSet().members(key);
    }
}

Cache Patterns

Cache-Aside Pattern

java

@Service
public class ProductService {
    
    @Autowired
    private ProductRepository productRepository;
    
    @Autowired
    private RedisTemplate<String, Object> redisTemplate;
    
    public Product getProduct(Long productId) {
        String cacheKey = "product:" + productId;
        
        // Check cache first
        Product cachedProduct = (Product) redisTemplate.opsForValue().get(cacheKey);
        if (cachedProduct != null) {
            return cachedProduct;
        }
        
        // Fetch from database
        Product product = productRepository.findById(productId).orElse(null);
        if (product != null) {
            // Add to cache
            redisTemplate.opsForValue().set(cacheKey, product, Duration.ofMinutes(30));
        }
        
        return product;
    }
    
    public Product updateProduct(Product product) {
        // Update database
        Product updatedProduct = productRepository.save(product);
        
        // Update cache
        String cacheKey = "product:" + product.getId();
        redisTemplate.opsForValue().set(cacheKey, updatedProduct, Duration.ofMinutes(30));
        
        return updatedProduct;
    }
}

Write-Through Pattern

java

@Service
public class WriteThoughCacheService {
    
    @Autowired
    private UserRepository userRepository;
    
    @Autowired
    private RedisTemplate<String, Object> redisTemplate;
    
    public User saveUser(User user) {
        // Write to database
        User savedUser = userRepository.save(user);
        
        // Write to cache (write-through)
        String cacheKey = "user:" + savedUser.getId();
        redisTemplate.opsForValue().set(cacheKey, savedUser, Duration.ofHours(1));
        
        return savedUser;
    }
}

Write-Behind (Write-Back) Pattern

java

@Service
public class WriteBehindCacheService {
    
    @Autowired
    private RedisTemplate<String, Object> redisTemplate;
    
    @Autowired
    private UserRepository userRepository;
    
    private final Queue<User> writeQueue = new ConcurrentLinkedQueue<>();
    
    public User updateUser(User user) {
        // Update cache immediately
        String cacheKey = "user:" + user.getId();
        redisTemplate.opsForValue().set(cacheKey, user, Duration.ofHours(1));
        
        // Queue database write operation
        writeQueue.offer(user);
        
        return user;
    }
    
    @Scheduled(fixedDelay = 5000) // Every 5 seconds
    public void flushToDatabase() {
        List<User> usersToWrite = new ArrayList<>();
        User user;
        
        while ((user = writeQueue.poll()) != null) {
            usersToWrite.add(user);
        }
        
        if (!usersToWrite.isEmpty()) {
            userRepository.saveAll(usersToWrite);
            log.info("Flushed {} users to database", usersToWrite.size());
        }
    }
}

Multi-Level Caching

Multi-Level Cache Features

L1 Cache (Local Memory)
- Fastest access time
- Application instance specific
- Limited memory capacity
L2 Cache (Distributed)
- Cluster-wide sharing
- Higher capacity
- Network latency impact
Database
- Used as last resort
- Complete data consistency
- Slowest access time

L1 (Local) + L2 (Distributed) Cache

java

@Service
public class MultiLevelCacheService {
    
    @Autowired
    private RedisTemplate<String, Object> redisTemplate;
    
    // L1 Cache - Local in-memory cache
    private final ConcurrentHashMap<String, CacheItem> localCache = new ConcurrentHashMap<>();
    
    public User getUser(Long userId) {
        String key = "user:" + userId;
        
        // L1 Cache check
        CacheItem item = localCache.get(key);
        if (item != null && !item.isExpired()) {
            return (User) item.getValue();
        }
        
        // L2 Cache check (Redis)
        User user = (User) redisTemplate.opsForValue().get(key);
        if (user != null) {
            localCache.put(key, new CacheItem(user, Duration.ofMinutes(5)));
            return user;
        }
        
        // Fetch from database
        user = userRepository.findById(userId).orElse(null);
        if (user != null) {
            // Add to both caches
            redisTemplate.opsForValue().set(key, user, Duration.ofMinutes(30));
            localCache.put(key, new CacheItem(user, Duration.ofMinutes(5)));
        }
        
        return user;
    }
    
    @Scheduled(fixedDelay = 60000) // Every minute
    public void cleanupLocalCache() {
        localCache.entrySet().removeIf(entry -> entry.getValue().isExpired());
    }
    
    private static class CacheItem {
        private final Object value;
        private final Instant expiry;
        
        public CacheItem(Object value, Duration ttl) {
            this.value = value;
            this.expiry = Instant.now().plus(ttl);
        }
        
        public Object getValue() { return value; }
        public boolean isExpired() { return Instant.now().isAfter(expiry); }
    }
}

Cache Invalidation Strategies

Event-Based Invalidation
- Automatic triggering on data changes
- Integration with event-driven architecture
- Selective cache clearing
Time-Based Invalidation
- TTL (Time-To-Live) based clearing
- Automatic cache refresh
- Simple and effective management
Manual Invalidation
- Admin control
- Emergency intervention
- Selective cache management

CDN Integration

Static Content Caching

java

@RestController
public class StaticContentController {
    
    @GetMapping(value = "/images/{filename}", produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
    public ResponseEntity<Resource> getImage(@PathVariable String filename) {
        try {
            Resource resource = resourceLoader.getResource("classpath:static/images/" + filename);
            
            return ResponseEntity.ok()
                .cacheControl(CacheControl.maxAge(Duration.ofDays(7))) // Cache for 7 days
                .eTag(calculateETag(resource))
                .body(resource);
        } catch (Exception e) {
            return ResponseEntity.notFound().build();
        }
    }
    
    @GetMapping("/api/products/{id}")
    public ResponseEntity<Product> getProduct(@PathVariable Long id) {
        Product product = productService.getProduct(id);
        
        return ResponseEntity.ok()
            .cacheControl(CacheControl.maxAge(Duration.ofMinutes(10)))
            .eTag(String.valueOf(product.getLastModified().hashCode()))
            .body(product);
    }
}

API Response Caching

java

@RestController
public class CachedApiController {
    
    @GetMapping("/api/popular-products")
    @Cacheable(value = "popular-products", unless = "#result.isEmpty()")
    public ResponseEntity<List<Product>> getPopularProducts() {
        List<Product> products = productService.getPopularProducts();
        
        return ResponseEntity.ok()
            .cacheControl(CacheControl.maxAge(Duration.ofMinutes(15)))
            .body(products);
    }
    
    @GetMapping("/api/categories")
    public ResponseEntity<List<Category>> getCategories(HttpServletRequest request) {
        String etag = categoryService.getCategoriesETag();
        
        // ETag check
        if (request.getHeader("If-None-Match") != null && 
            request.getHeader("If-None-Match").equals(etag)) {
            return ResponseEntity.status(HttpStatus.NOT_MODIFIED).build();
        }
        
        List<Category> categories = categoryService.getAllCategories();
        
        return ResponseEntity.ok()
            .eTag(etag)
            .cacheControl(CacheControl.maxAge(Duration.ofHours(1)))
            .body(categories);
    }
}

Performance Monitoring

Cache Metrics

java

@Component
public class CacheMetrics {
    
    private final MeterRegistry meterRegistry;
    private final Counter cacheHits;
    private final Counter cacheMisses;
    private final Timer cacheLoadTime;
    
    public CacheMetrics(MeterRegistry meterRegistry) {
        this.meterRegistry = meterRegistry;
        this.cacheHits = Counter.builder("cache.hits")
            .tag("cache", "users")
            .register(meterRegistry);
        this.cacheMisses = Counter.builder("cache.misses")
            .tag("cache", "users")
            .register(meterRegistry);
        this.cacheLoadTime = Timer.builder("cache.load.time")
            .register(meterRegistry);
    }
    
    public void recordCacheHit(String cacheName) {
        cacheHits.increment(Tags.of("cache", cacheName));
    }
    
    public void recordCacheMiss(String cacheName) {
        cacheMisses.increment(Tags.of("cache", cacheName));
    }
    
    public void recordCacheLoadTime(Duration duration) {
        cacheLoadTime.record(duration);
    }
}

Cache Health Monitoring

java

@Component
public class CacheHealthIndicator implements HealthIndicator {
    
    @Autowired
    private RedisTemplate<String, Object> redisTemplate;
    
    @Override
    public Health health() {
        try {
            redisTemplate.opsForValue().set("health-check", "ping", Duration.ofSeconds(10));
            String response = (String) redisTemplate.opsForValue().get("health-check");
            
            if ("ping".equals(response)) {
                return Health.up()
                    .withDetail("redis", "Available")
                    .withDetail("responseTime", measureResponseTime() + "ms")
                    .build();
            } else {
                return Health.down()
                    .withDetail("redis", "Invalid response")
                    .build();
            }
        } catch (Exception e) {
            return Health.down()
                .withDetail("redis", "Unavailable")
                .withException(e)
                .build();
        }
    }
    
    private long measureResponseTime() {
        long start = System.currentTimeMillis();
        redisTemplate.opsForValue().get("health-check");
        return System.currentTimeMillis() - start;
    }
}

Production Best Practices

Cache Warming

java

@Component
public class CacheWarmupService {
    
    @Autowired
    private ProductService productService;
    
    @Autowired
    private UserService userService;
    
    @EventListener(ApplicationReadyEvent.class)
    public void warmupCache() {
        log.info("Starting cache warmup...");
        
        CompletableFuture.runAsync(this::warmupPopularProducts);
        CompletableFuture.runAsync(this::warmupFrequentlyAccessedUsers);
        
        log.info("Cache warmup initiated");
    }
    
    private void warmupPopularProducts() {
        List<Long> popularProductIds = getPopularProductIds();
        popularProductIds.forEach(productService::getProduct);
        log.info("Warmed up {} popular products", popularProductIds.size());
    }
    
    private void warmupFrequentlyAccessedUsers() {
        List<Long> frequentUserIds = getFrequentlyAccessedUserIds();
        frequentUserIds.forEach(userService::getUserById);
        log.info("Warmed up {} frequently accessed users", frequentUserIds.size());
    }
}

Cache Disaster Recovery

java

@Service
public class CacheDisasterRecoveryService {
    
    @Autowired
    private RedisTemplate<String, Object> primaryRedis;
    
    @Autowired
    private RedisTemplate<String, Object> backupRedis;
    
    @Retryable(value = Exception.class, maxAttempts = 3)
    public Object getCachedValue(String key) {
        try {
            return primaryRedis.opsForValue().get(key);
        } catch (Exception e) {
            log.warn("Primary Redis failed, trying backup: {}", e.getMessage());
            return backupRedis.opsForValue().get(key);
        }
    }
    
    @Async
    public void syncCaches() {
        Set<String> keys = primaryRedis.keys("*");
        for (String key : keys) {
            try {
                Object value = primaryRedis.opsForValue().get(key);
                Long ttl = primaryRedis.getExpire(key);
                
                if (ttl > 0) {
                    backupRedis.opsForValue().set(key, value, Duration.ofSeconds(ttl));
                }
            } catch (Exception e) {
                log.error("Failed to sync cache key {}: {}", key, e.getMessage());
            }
        }
    }
}

These caching strategies significantly improve system performance and reduce database load. With Redis distributed caching, multi-level cache structures, and proper invalidation strategies, they provide production-ready caching solutions.

Cache-Through and Database-Through Terminology

“Cache-through” should not be treated as one precise pattern name; describe the flow explicitly:

Pattern	Read/write flow	Source of truth
Cache-aside	Application reads the DB on a miss and fills the cache	DB
Read-through	Cache provider calls a DB loader on a miss	DB
Write-through	A write through the cache synchronously updates the DB	DB
Write-behind	Cache is updated first and the DB is updated asynchronously	DB, delayed
Direct DB / DB-through	Cache is bypassed and the DB is read or written directly	DB

The cache is a speed layer. Unless explicitly designed otherwise, the database remains the source of truth. Document invalidation, TTL, stale reads, stampedes, hot keys, and failover behavior with the selected pattern.

Pattern Selection Check

Which layer calls the DB on a cache miss?
Can a response be returned before the DB succeeds?
Does a failed cache write make the mutation fail?
Are duplicate writes and retries idempotent?
Can the origin handle traffic if the cache disappears?

Caching - Spring Boot Multi-Layer Approach ​

Quick Decision ​

Production Checklist ​

Cache Architecture Overview ​

Cache Patterns ​

Cache Pattern Descriptions ​

Distributed Cache Architecture ​

Application-Level Caching ​

Spring Cache Abstraction ​

Basic Cache Configuration ​

Cache Annotations ​

Redis Distributed Caching ​

Redis Configuration ​

Manual Cache Operations ​

Cache Patterns ​

Cache-Aside Pattern ​

Write-Through Pattern ​

Write-Behind (Write-Back) Pattern ​

Multi-Level Caching ​

Multi-Level Cache Features ​

L1 (Local) + L2 (Distributed) Cache ​

Cache Invalidation Strategies ​

Cache Invalidation Strategies ​

CDN Integration ​

Static Content Caching ​

API Response Caching ​

Performance Monitoring ​

Cache Metrics ​

Cache Health Monitoring ​

Production Best Practices ​

Cache Warming ​

Cache Disaster Recovery ​

Cache-Through and Database-Through Terminology ​

Pattern Selection Check ​

Caching - Spring Boot Multi-Layer Approach

Quick Decision

Production Checklist

Cache Architecture Overview

Cache Patterns

Cache Pattern Descriptions

Distributed Cache Architecture

Application-Level Caching

Spring Cache Abstraction

Basic Cache Configuration

Cache Annotations

Redis Distributed Caching

Redis Configuration

Manual Cache Operations

Cache Patterns

Cache-Aside Pattern

Write-Through Pattern

Write-Behind (Write-Back) Pattern

Multi-Level Caching

Multi-Level Cache Features

L1 (Local) + L2 (Distributed) Cache

Cache Invalidation Strategies

Cache Invalidation Strategies

CDN Integration

Static Content Caching

API Response Caching

Performance Monitoring

Cache Metrics

Cache Health Monitoring

Production Best Practices

Cache Warming

Cache Disaster Recovery

Cache-Through and Database-Through Terminology

Pattern Selection Check