Why caching improves response times in Ruby on Rails - Performance Evidence

Performance: Why caching improves response times

HIGH IMPACT

Caching reduces server processing time and network delays, speeding up page load and interaction response.

Serving frequently requested data in a Rails app

Ruby on Rails

def show
  @post = Rails.cache.fetch("post_#{params[:id]}") { Post.find(params[:id]) }
  render json: @post
end

Caches the post data after first fetch, serving subsequent requests instantly.

📈 Performance GainReduces DB queries to zero for cached items, cutting response time by ~80%

Serving frequently requested data in a Rails app

Ruby on Rails

def show
  @post = Post.find(params[:id])
  render json: @post
end

Every request queries the database, causing slow response and high server load.

📉 Performance CostBlocks rendering for 50-100ms per request depending on DB speed

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
No caching, fetch from DB every time	N/A (server-side)	N/A	N/A	[X] Bad
Cache data with Rails.cache.fetch	N/A (server-side)	N/A	N/A	[OK] Good

Rendering Pipeline

Caching bypasses repeated server-side data fetching and processing, delivering precomputed content quickly to the browser.

→Server Processing

→Network Transfer

→Browser Rendering

⚠️ BottleneckServer Processing (database queries and rendering)

Core Web Vital Affected

LCP

Caching reduces server processing time and network delays, speeding up page load and interaction response.

Optimization Tips

1Cache frequently requested data to reduce server processing time.

2Use Rails.cache.fetch to store and retrieve cached content efficiently.

3Monitor cache hit rates to ensure caching is effective.

Performance Quiz - 3 Questions

How does caching improve response times in a Rails app?

A By delaying server responses intentionally

B By increasing the number of database queries

C By storing data to avoid repeated database queries

D By removing CSS from the page

DevTools: Network

How to check: Open DevTools > Network tab, reload page, and observe response times and headers for cached content.

What to look for: Look for faster response times and cache-related headers like 'X-Cache' or reduced server processing time.