Why caching matters in Node.js - Performance Evidence

Performance: Why caching matters

HIGH IMPACT

Caching improves page load speed and reduces server response time by storing data closer to the user or in memory.

Serving frequently requested data in a Node.js app

Node.js

const cache = new Map();
app.get('/data', async (req, res) => {
  if (cache.has('data')) {
    return res.json(cache.get('data'));
  }
  const data = await fetchFromDatabase();
  cache.set('data', data);
  res.json(data);
});

Caches data in memory to serve repeated requests instantly without database calls.

📈 Performance GainReduces response time to under 10 ms, lowers server CPU usage significantly

Serving frequently requested data in a Node.js app

Node.js

app.get('/data', async (req, res) => {
  const data = await fetchFromDatabase();
  res.json(data);
});

Every request hits the database causing slow responses and high server load.

📉 Performance CostBlocks rendering for 100+ ms per request, increases server CPU usage

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
No caching, fetch on every request	N/A	N/A	High due to slow data arrival	[X] Bad
In-memory caching for repeated data	N/A	N/A	Low, data served instantly	[OK] Good

Rendering Pipeline

Caching reduces the time spent waiting for server data, allowing the browser to start rendering sooner.

→Network

→Server Processing

→First Paint

⚠️ BottleneckServer Processing time waiting for database or API response

Core Web Vital Affected

LCP

Caching improves page load speed and reduces server response time by storing data closer to the user or in memory.

Optimization Tips

1Cache frequently requested data to reduce server response time.

2Use in-memory or CDN caches to serve repeated requests faster.

3Avoid unnecessary database calls to improve LCP and reduce server load.

Performance Quiz - 3 Questions

How does caching improve Largest Contentful Paint (LCP)?

A By serving data faster, reducing server wait time

B By reducing CSS complexity

C By decreasing JavaScript bundle size

D By avoiding layout shifts

DevTools: Network

How to check: Open DevTools, go to Network tab, reload page and observe response times for repeated requests.

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