@Component annotation in Spring Boot - Performance & Optimization

Performance: @Component annotation

MEDIUM IMPACT

This affects application startup time and memory usage by controlling bean creation and dependency injection.

Registering a Spring bean for dependency injection

Spring Boot

@Component
@Lazy
public class HeavyService {
    public HeavyService() {
        // expensive initialization
    }
}

Delays bean creation until first use, reducing startup time and memory usage initially.

📈 Performance GainSpeeds startup by avoiding unnecessary bean instantiation, saves memory until needed

Registering a Spring bean for dependency injection

Spring Boot

@Component
public class HeavyService {
    public HeavyService() {
        // expensive initialization
    }
}

Creates a heavy bean eagerly at startup even if not used immediately, increasing startup time and memory.

📉 Performance CostBlocks application startup for extra milliseconds, increases memory footprint

Performance Comparison

Pattern	Bean Creation	Startup Delay	Memory Usage	Verdict
Eager @Component	Creates all beans at startup	High delay if many heavy beans	High memory usage	[X] Bad
@Component with @Lazy	Creates beans on demand	Minimal startup delay	Lower memory usage initially	[OK] Good

Rendering Pipeline

Spring scans for @Component annotations during startup, creating and wiring beans before the app runs.

→Bean Creation

→Dependency Injection

→Application Startup

⚠️ BottleneckBean Creation stage can delay startup if many or heavy beans are created eagerly.

Optimization Tips

1Avoid creating heavy beans eagerly with @Component to reduce startup time.

2Use @Lazy on @Component beans to defer creation until needed.

3Monitor bean creation times to identify startup bottlenecks.

Performance Quiz - 3 Questions

What is the main performance impact of using @Component without @Lazy in Spring Boot?

A All beans are created eagerly at startup, increasing startup time and memory use.

B Beans are created only when first used, reducing startup time.

C Beans are never created, causing runtime errors.

D Beans are created in parallel, improving startup speed.

DevTools: Spring Boot Actuator / Logs

How to check: Enable debug logging for Spring context startup and monitor bean creation times.

What to look for: Look for long bean creation times or many beans created eagerly indicating startup bottlenecks.