Performance Tuning

Optimize Spring Boot application performance — JVM tuning, connection pool sizing, caching, async processing, virtual threads, and common performance anti-patterns.

@Configuration
@EnableCaching
public class CacheConfig {

    @Bean
    public CacheManager cacheManager(RedisConnectionFactory factory) {
        RedisCacheConfiguration config = RedisCacheConfiguration.defaultCacheConfig()
            .entryTtl(Duration.ofMinutes(10))
            .disableCachingNullValues()
            .serializeValuesWith(
                RedisSerializationContext.SerializationPair
                    .fromSerializer(new GenericJackson2JsonRedisSerializer()));

        return RedisCacheManager.builder(factory)
            .cacheDefaults(config)
            .withCacheConfiguration("products",
                config.entryTtl(Duration.ofHours(1)))  // products cached 1 hour
            .withCacheConfiguration("user-sessions",
                config.entryTtl(Duration.ofMinutes(30)))
            .build();
    }
}

@Service
public class ProductService {

    // Cache result — subsequent calls return cached value without DB
    @Cacheable(value = "products", key = "#id")
    public ProductDto getProduct(Long id) {
        return productRepository.findById(id)  // Only called on cache miss
            .map(ProductDto::from)
            .orElseThrow(() -> new ResourceNotFoundException("Product", id));
    }

    // Evict cache when product is updated
    @CacheEvict(value = "products", key = "#id")
    @Transactional
    public ProductDto updateProduct(Long id, UpdateProductRequest request) {
        // Cache cleared — next getProduct call hits DB
        return productRepository.findById(id)
            .map(p -> { p.update(request); return productRepository.save(p); })
            .map(ProductDto::from)
            .orElseThrow(() -> new ResourceNotFoundException("Product", id));
    }
}

The 80/20 rule of Spring Boot performance: 80% of performance issues come from database problems. Before tuning JVM or adding caching, check your queries. Enable slow query logging (log queries > 100ms), run EXPLAIN ANALYZE on slow queries, add missing indexes. A single missing index fix can improve performance 100x. Only then consider caching and async processing.