ls projects/

1@Service
2@RequiredArgsConstructor
3public class ProductCacheService {
4
5    private final RedissonClient redissonClient;
6    private final Cache<Long, ProductDTO> caffeineCache;
7
8    @Cacheable(value = "products", key = "#id")
9    public ProductDTO getProductById(Long id) {
10        // L1: Check Caffeine (1-5ms)
11        ProductDTO cached = caffeineCache.getIfPresent(id);
12        if (cached != null) return cached;
13
14        // L2: Check Redis with distributed lock
15        RLock lock = redissonClient.getLock("lock:product:" + id);
16        try {
17            if (lock.tryLock(5, 10, TimeUnit.SECONDS)) {
18                // Only 1 thread queries DB (prevents stampede)
19                ProductDTO product = fetchFromDatabase(id);
20                caffeineCache.put(id, product);
21                return product;
22            }
23        } finally {
24            lock.unlock();
25        }
26        return fetchFromDatabase(id);
27    }
28}