Cache stores (memory, Redis) in NestJS - Performance & Optimization

Performance: Cache stores (memory, Redis)

HIGH IMPACT

This affects how fast data can be retrieved and reduces server processing time, improving response speed and user experience.

Storing frequently accessed data to speed up responses

NestJS

async getUser(id: string) {
  const cached = await this.cacheManager.get(id);
  if (cached) return cached;
  const user = await this.userService.findById(id);
  await this.cacheManager.set(id, user, { ttl: 300 });
  return user;
}

Caches data in memory or Redis to serve repeated requests instantly.

📈 Performance GainReduces DB calls by 90%, cuts response time to under 20 ms

Storing frequently accessed data to speed up responses

NestJS

async getUser(id: string) {
  return await this.userService.findById(id); // Always fetches from DB
}

Fetching from the database every time causes slow responses and high server load.

📉 Performance CostBlocks rendering for 100+ ms per request under load

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
No cache (DB fetch every time)	N/A	N/A	High server delay causes slow paint	[X] Bad
In-memory cache store	N/A	N/A	Fast response reduces paint delay	[OK] Good
Redis cache store	N/A	N/A	Fast network cache reduces paint delay	[OK] Good

Rendering Pipeline

Cache stores reduce server processing time before the response reaches the browser, speeding up the critical rendering path.

→Server Processing

→Network Transfer

→First Contentful Paint

⚠️ BottleneckServer Processing time waiting for data fetch

Core Web Vital Affected

LCP

This affects how fast data can be retrieved and reduces server processing time, improving response speed and user experience.

Optimization Tips

1Cache frequently requested data to reduce server processing time.

2Use Redis for distributed caching to keep data consistent across servers.

3Avoid cache misses by setting appropriate TTL and warming cache when possible.

Performance Quiz - 3 Questions

How does using a Redis cache store affect page load performance?

A It reduces server processing time by serving cached data quickly

B It increases DOM nodes causing slower rendering

C It blocks the main thread during cache retrieval

D It causes more layout shifts on the page

DevTools: Network

How to check: Open DevTools > Network tab, reload page, check response times for API calls

What to look for: Look for reduced response times and fewer database query calls indicating cache hits