@RestController annotation in Spring Boot - Performance & Optimization

Performance: @RestController annotation

MEDIUM IMPACT

This affects server response time and client perceived load speed by simplifying REST API endpoint creation.

Creating REST API endpoints in Spring Boot

Spring Boot

@RestController
public class MyController {
  @RequestMapping("/data")
  public String getData() {
    return "Hello";
  }
}

Combines @Controller and @ResponseBody, reducing annotation overhead and ensuring consistent JSON or text responses.

📈 Performance GainReduces server processing steps, improving response time and lowering LCP.

Creating REST API endpoints in Spring Boot

Spring Boot

@Controller
public class MyController {
  @RequestMapping("/data")
  @ResponseBody
  public String getData() {
    return "Hello";
  }
}

Separately using @Controller and @ResponseBody adds boilerplate and can lead to inconsistent response handling.

📉 Performance CostSlightly increased server processing due to extra annotation handling and potential misconfiguration.

Performance Comparison

Pattern	Server Processing	Annotation Overhead	Response Consistency	Verdict
@Controller + @ResponseBody	Moderate	Higher due to multiple annotations	Consistent if used correctly	[!] OK
@RestController	Lower	Minimal, combined annotation	Always consistent JSON/text response	[OK] Good

Rendering Pipeline

The @RestController annotation affects the server-side processing before the browser rendering pipeline starts. It streamlines response generation, reducing server response time which impacts the browser's Largest Contentful Paint (LCP).

→Server Processing

→Network Transfer

→Browser Rendering

⚠️ BottleneckServer Processing stage due to response serialization and annotation handling

Core Web Vital Affected

LCP

This affects server response time and client perceived load speed by simplifying REST API endpoint creation.

Optimization Tips

1Use @RestController to combine @Controller and @ResponseBody for faster server responses.

2Reducing server annotation overhead improves LCP by speeding up content delivery.

3Consistent JSON or text responses from @RestController avoid extra processing delays.

Performance Quiz - 3 Questions

How does using @RestController improve performance compared to @Controller with @ResponseBody?

A It combines annotations to reduce server processing overhead.

B It caches responses automatically to speed up loading.

C It compresses the response payload to reduce size.

D It delays response until all data is fully processed.

DevTools: Network

How to check: Open DevTools, go to Network tab, reload the API endpoint, and check the response time and payload size.

What to look for: Look for faster response times and consistent JSON or text responses indicating efficient server processing.