Redis caching

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Goal

Add Redis caching to the service layer. Frequently-read items are cached in Redis to reduce database load.

Prerequisites

• OpenAPI documentation

Dependency

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

Enable caching

@Configuration
@EnableCaching
public class CacheConfig {

    @Bean
    public RedisCacheManager cacheManager(RedisConnectionFactory factory) {
        var config = RedisCacheConfiguration.defaultCacheConfig()
            .entryTtl(Duration.ofMinutes(10));
        return RedisCacheManager.builder(factory)
            .cacheDefaults(config)
            .build();
    }
}

Cache the service layer

@Service
public class ItemService {

    @Cacheable("items")
    public List<Item> list() {
        // This method is called only on cache miss
        return repository.findAll();
    }

    @CacheEvict(value = "items", allEntries = true)
    public Item create(Item item) {
        return repository.save(item);
    }

    @CacheEvict(value = "items", key = "#id")
    public void delete(Long id) {
        repository.deleteById(id);
    }
}

Redis configuration

application-prod.properties:

spring.data.redis.host=redis
spring.data.redis.port=6379

Add Redis to docker-compose

services:
  # ... app and db services ...
  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"
    healthcheck:
      test: ["CMD", "redis-cli", "ping"]
      interval: 3s
      retries: 5

Update depends_on for the app service:

  app:
    depends_on:
      db: { condition: service_healthy }
      redis: { condition: service_healthy }

Verify caching

# First request — hits database
time curl http://localhost:8080/items
# ~200ms

# Second request — cached
time curl http://localhost:8080/items
# ~5ms (cache hit, no DB query)

Monitor with Redis CLI:

docker exec -it learning-docs-redis-1 redis-cli
127.0.0.1:6379> keys *
# 1) "items::SimpleKey []"
127.0.0.1:6379> TTL "items::SimpleKey []"
# (integer) 542  (seconds remaining)

Checkpoint

# First request: slow (cache miss)
curl http://localhost:8080/items
# Second request: instant (cache hit)
curl http://localhost:8080/items
# Create a new item — cache evicted
curl -X POST -H "Content-Type: application/json" \
  -d '{"title":"new"}' http://localhost:8080/items

Next: Actuator and health — production monitoring endpoints.