Caching and CDN

1. 💾 Caching and CDN

Caching Overview

Purpose: Improves system performance and efficiency Involves storing temporary data copies in cache

1.1. 🔄 Common Caching Locations

1. Browser Caching

• Local Storage:
  • Stores data locally instead of server requests
  • Configurable via browser developer tools

Header Controls:

• max-age: Defines cache duration
• stale-if-error: Fallback behavior
• stale-while-revalidate: Background refresh strategy

Metrics: \(Cache Ratio = Cache Hits \div (Cache Hits + Cache Misses)\)

2. Server Caching

• Storage Options:
  • Server-side storage
  • Separate cache servers
  • In-memory (Redis) or disk storage

Caching Strategies:

1. Write-around:

   • Direct storage writing
   • Best for cases where data freshness is critical

2. Write-through:

   • Simultaneous cache/storage updates
   • Ensures data consistency
   • Can be slower than write-around

3. Write-back:

   • Cache-first approach, then to permanent storage
   • Risk of data loss during crashes

Eviction Policies:

• LRU (Least Recently Used)
• FIFO (First In First Out)
• LFU (Least Frequently Used)

3. Database Caching

• Implementation:
  • Internal database system
  • External cache layer (Redis/Memcache)

Process Flow:

1. Check cache first
2. Return cached data if present
3. Execute query if cache miss
4. Store new results in cache

Optimal for read-heavy applications

Uses same eviction policies as server caching

4. CDN (Content Delivery Networks)

Purpose: Distributed server network for static content delivery

Request Flow:

1. User requests resource
2. Request redirects to nearest CDN server
3. If cached, delivers content
4. If not cached, fetches from origin server, caches, and delivers

Content Types:

• JavaScript
• HTML/CSS
• Images/Videos

Distribution Strategies:

1. Pull-based:

   • Automatic content pulling
   • Ideal for frequently updated static content
   • Self-managing updates

2. Push-based:

   • Manual content distribution
   • Best for large, infrequently updated files
   • Requires active management

Control:

• Cache-Control header defines cache duration

1.2. 🌐 When to Use Each Solution

Use CDN When

1. Content Type:

• Static assets delivery
  • Images
  • CSS files
  • JavaScript files
  • Video content

2. Requirements:

• Global user base
• High availability needs
• Origin server load reduction

Use Origin Server When

1. Dynamic Content:

• Frequently changing data
• Personalized user content

2. Real-time Processing:

• Time-critical operations
• Up-to-date data access

3. Complex Operations:

• Advanced server-side logic
• Non-cacheable processes

1.3. Benefits Breakdown

CDN Advantages

1. Reduced Latency

   • Geographically closer servers
   • Faster content delivery

2. High Availability

   • Better load handling
   • Distributed traffic

3. Enhanced Security

   • DDOS protection
   • Security features included

Caching Advantages

1. Reduced Latency

   • Quick data access
   • Faster response times

2. Server Optimisation

   • Lower resource usage
   • Reduced database load

3. Better UX

   • Faster page loads
   • Smoother interactions