What are key performance optimization techniques for Spring Boot applications? Spring Boot applications के लिए performance optimization techniques क्या हैं?

Optimize through connection pooling, caching, async processing, lazy loading, database indexing, and HTTP caching headers. Profile applications to identify bottlenecks. Use tools like JProfiler for memory and CPU analysis.

// 1. Database Connection Pooling (HikariCP)
spring:
  datasource:
    hikari:
      maximum-pool-size: 20
      minimum-idle: 5
      connection-timeout: 30000
      idle-timeout: 600000
      max-lifetime: 1800000

// 2. Caching Strategy
@Configuration
@EnableCaching
public class CacheConfig {
    @Bean
    public CacheManager cacheManager() {
        CaffeineCacheManager cacheManager = new CaffeineCacheManager();
        cacheManager.setCaffeine(Caffeine.newBuilder()
            .expireAfterWrite(10, TimeUnit.MINUTES)
            .maximumSize(1000));
        return cacheManager;
    }
}

@Service
public class ProductService {
    @Cacheable(value = 'products', key = '#id')
    public Product getProduct(Long id) {
        // Database query - cached after first call
        return productRepository.findById(id).orElse(null);
    }
}

// 3. Lazy Loading
@Entity
public class Order {
    @OneToMany(fetch = FetchType.LAZY)
    private List<OrderItem> items;  // Loaded only when accessed
}

// 4. Database Indexing
@Entity
public class User {
    @Id
    private Long id;
    
    @Column(unique = true)
    @Index(name = 'idx_email')
    private String email;  // Index for faster queries
}

// 5. HTTP Caching Headers
@RestController
public class ContentController {
    @GetMapping('/api/static')
    public ResponseEntity<Content> getStatic() {
        return ResponseEntity.ok()
            .cacheControl(CacheControl.maxAge(1, TimeUnit.HOURS)
                .cachePublic())
            .body(content);
    }
}

// 6. Compression
server:
  compression:
    enabled: true
    min-response-size: 1024
    mime-types: application/json,text/html,text/xml

// 7. Thread Pool Configuration
@Configuration
public class ThreadPoolConfig {
    @Bean(name = 'taskExecutor')
    public Executor taskExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(10);
        executor.setMaxPoolSize(20);
        executor.setQueueCapacity(100);
        executor.setThreadNamePrefix('async-');
        executor.initialize();
        return executor;
    }
}

// 8. Database Query Optimization
@Repository
public interface OrderRepository extends JpaRepository<Order, Long> {
    // N+1 query problem - use JOIN FETCH
    @Query('SELECT DISTINCT o FROM Order o LEFT JOIN FETCH o.items WHERE o.customerId = ?1')
    List<Order> findByCustomerIdOptimized(Long customerId);
}

// 9. Profiling and Monitoring
// JProfiler, YourKit, or JFR (Java Flight Recorder)
java -XX:+UnlockCommercialFeatures -XX:+FlightRecorder \
     -XX:StartFlightRecording=delay=20s,duration=60s,filename=recording.jfr \
     -jar app.jar

// 10. GC Optimization
# application.properties
spring.jvm.args=-XX:+UseG1GC -XX:MaxGCPauseMillis=200

// Benchmark Results (before/after optimization):
// Response time: 500ms -> 50ms (10x faster)
// Memory usage: 800MB -> 200MB
// QPS: 100 -> 1000