Controller decorator in NestJS - Performance & Optimization

Performance: Controller decorator

MEDIUM IMPACT

This affects the routing setup and initial request handling speed in a NestJS application.

Defining routes for handling HTTP requests in a NestJS app

NestJS

import { Controller, Get } from '@nestjs/common';

@Controller('api')
export class AppController {
  @Get('users')
  getUsers() {
    // logic
  }

  @Get('products')
  getProducts() {
    // logic
  }

  @Get('orders')
  getOrders() {
    // logic
  }
}

Prefixing routes with a common path segment reduces routing complexity and speeds up route matching.

📈 Performance GainReduces routing checks per request, improving INP by lowering request handling latency.

Defining routes for handling HTTP requests in a NestJS app

NestJS

import { Controller, Get } from '@nestjs/common';

@Controller('')
export class AppController {
  @Get('users')
  getUsers() {
    // logic
  }

  @Get('products')
  getProducts() {
    // logic
  }

  @Get('orders')
  getOrders() {
    // logic
  }
}

Using an empty string in @Controller decorator causes all routes to be registered at the root, increasing routing checks and complexity.

📉 Performance CostAdds unnecessary routing overhead, increasing request matching time slightly for each route.

Performance Comparison

Pattern	Routing Checks	Request Latency	Code Complexity	Verdict
Empty string prefix in @Controller	High (all routes at root)	Higher latency due to more checks	Moderate	[X] Bad
Specific prefix in @Controller (e.g., 'api')	Lower (grouped routes)	Lower latency with faster matching	Moderate	[OK] Good

Rendering Pipeline

The Controller decorator defines route prefixes that the NestJS router uses to match incoming HTTP requests. Efficient route prefixing reduces the number of checks the router performs before invoking the handler.

→Routing

→Request Handling

⚠️ BottleneckRouting stage due to inefficient route matching

Core Web Vital Affected

INP

This affects the routing setup and initial request handling speed in a NestJS application.

Optimization Tips

1Always use specific route prefixes in @Controller to group related routes.

2Avoid empty or overly broad prefixes that cause routing overhead.

3Keep route definitions clear to minimize routing checks and improve responsiveness.

Performance Quiz - 3 Questions

How does using a specific prefix in the @Controller decorator affect routing performance?

A It reduces routing checks by grouping routes under a common path.

B It increases routing checks by adding more routes.

C It has no effect on routing performance.

D It blocks rendering until all routes are loaded.

DevTools: Network and Performance panels

How to check: Use the Network panel to measure response times for API calls. Use the Performance panel to record and analyze request handling duration.

What to look for: Look for lower request latency and faster handler invocation times indicating efficient routing.