Handling not found exceptions in Spring Boot - Performance & Optimization

Performance: Handling not found exceptions

MEDIUM IMPACT

This affects server response time and user experience by controlling how quickly and cleanly the server handles missing resource requests.

Handling a missing resource request in a REST API

Spring Boot

@ResponseStatus(HttpStatus.NOT_FOUND)
public class ResourceNotFoundException extends RuntimeException {}

@GetMapping("/resource/{id}")
public ResponseEntity<Resource> getResource(@PathVariable String id) {
  return repository.findById(id)
    .map(ResponseEntity::ok)
    .orElseThrow(ResourceNotFoundException::new);
}

Throws specific exception early, allowing Spring Boot to handle 404 response efficiently without extra processing.

📈 Performance Gainreduces server processing time by 50-100ms, improving LCP

Handling a missing resource request in a REST API

Spring Boot

try {
  // fetch resource
} catch (Exception e) {
  return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Error occurred");
}

Catching generic exceptions causes unclear error handling and may block response with unnecessary processing.

📉 Performance Costblocks response generation longer, increasing LCP by 100-200ms

Performance Comparison

Pattern	Server Processing	Response Delay	Network Impact	Verdict
Generic Exception Catching	High (extra processing)	Increased by 100-200ms	No impact	[X] Bad
Specific NotFound Exception	Low (early exit)	Minimal delay	No impact	[OK] Good

Rendering Pipeline

When a resource is not found, the server generates a 404 response quickly, avoiding extra processing that delays the response body rendering.

→Server Processing

→Response Generation

→Network Transfer

⚠️ BottleneckServer Processing when exceptions are handled inefficiently

Core Web Vital Affected

LCP

This affects server response time and user experience by controlling how quickly and cleanly the server handles missing resource requests.

Optimization Tips

1Use specific exceptions for not found cases to enable fast 404 responses.

2Avoid catching generic exceptions that delay response generation.

3Leverage Spring Boot's @ResponseStatus to simplify and speed up error handling.

Performance Quiz - 3 Questions

What is the main performance benefit of using a specific NotFound exception in Spring Boot?

A It increases the bundle size but improves UI rendering.

B It allows the server to quickly return a 404 response without extra processing.

C It delays the response to log more details.

D It triggers multiple reflows in the browser.

DevTools: Network

How to check: Open DevTools, go to Network tab, filter for the API request, and check the response status and timing.

What to look for: Look for 404 status with minimal response time indicating efficient not found handling.