Applying middleware to routes in NestJS - Performance & Optimization

Performance: Applying middleware to routes

MEDIUM IMPACT

Middleware affects the request processing speed and can impact the time before the route handler executes, influencing interaction responsiveness.

Applying middleware to all routes indiscriminately

NestJS

app.use('/api/users', userMiddleware); // applies middleware only to /api/users routes

Middleware runs only on targeted routes, reducing unnecessary processing and improving responsiveness.

📈 Performance Gainreduces middleware executions, lowering INP latency

Applying middleware to all routes indiscriminately

NestJS

app.use(globalMiddleware); // applies middleware to every route

Middleware runs on every request, even when not needed, causing unnecessary processing and slower response times.

📉 Performance Costadds processing overhead on every request, increasing INP latency

Performance Comparison

Pattern	Middleware Runs	Processing Overhead	Response Delay	Verdict
Global middleware on all routes	Every request	High	Increased INP latency	[X] Bad
Middleware applied to specific routes	Only targeted requests	Low	Minimal delay	[OK] Good

Rendering Pipeline

Middleware runs during the server request lifecycle before the route handler, affecting how fast the server can respond to user input.

→Request Processing

→Route Matching

→Handler Execution

⚠️ BottleneckMiddleware processing time before route handler

Core Web Vital Affected

INP

Middleware affects the request processing speed and can impact the time before the route handler executes, influencing interaction responsiveness.

Optimization Tips

1Apply middleware only to routes that require it to reduce processing overhead.

2Keep middleware logic lightweight to minimize request handling delay.

3Avoid global middleware unless absolutely necessary to improve input responsiveness.

Performance Quiz - 3 Questions

What is the main performance risk of applying middleware globally to all routes in NestJS?

A Middleware runs on every request, causing unnecessary processing.

B Middleware reduces bundle size.

C Middleware improves LCP by preloading data.

D Middleware eliminates layout shifts.

DevTools: Network

How to check: Open DevTools Network panel, filter requests by route, and compare response times with and without middleware.

What to look for: Look for increased response time on routes with middleware indicating processing overhead.