Cache decorators in NestJS - Performance & Optimization

Performance: Cache decorators

MEDIUM IMPACT

Cache decorators improve response time by storing results and reducing repeated processing, impacting page load speed and interaction responsiveness.

Caching results of a controller method to speed up repeated requests

NestJS

@UseInterceptors(CacheInterceptor)
async getData() {
  return await this.service.fetchData();
}

Caches the result after first call, serving subsequent requests instantly without recomputation.

📈 Performance GainReduces server processing time and response delay, improving INP significantly

Caching results of a controller method to speed up repeated requests

NestJS

async getData() {
  // heavy computation or DB call
  return await this.service.fetchData();
}

Every request triggers the full computation or database call, causing slower responses and higher server load.

📉 Performance CostBlocks response for full computation on every request, increasing INP and server CPU usage

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
No caching	N/A	N/A	N/A	[X] Bad
With cache decorators	N/A	N/A	N/A	[OK] Good

Rendering Pipeline

Cache decorators intercept method calls to serve cached data instead of recomputing, reducing backend processing before sending response to browser.

→Server Processing

→Network Transfer

⚠️ BottleneckServer Processing (heavy computation or DB calls)

Core Web Vital Affected

INP

Cache decorators improve response time by storing results and reducing repeated processing, impacting page load speed and interaction responsiveness.

Optimization Tips

1Cache results of expensive methods to reduce server processing time.

2Use cache decorators to serve repeated requests instantly.

3Monitor response times in Network tab to verify caching effectiveness.

Performance Quiz - 3 Questions

How do cache decorators improve web app performance?

A By delaying server responses intentionally

B By increasing the number of DOM nodes rendered

C By storing method results to serve repeated requests faster

D By adding extra CSS styles to speed up rendering

DevTools: Network

How to check: Open DevTools, go to Network tab, make repeated requests to the endpoint and observe response times.

What to look for: Faster response times on repeated requests indicate effective caching.