# Content Delivery Network (CDN)

Quick Reference: Cache | Replacement Policy

# Quick Reference

# Clear Definition

CDN (Content Delivery Network) is a distributed network of servers that cache content geographically close to users, reducing latency and improving performance.

💡 Key Insight: CDNs cache static and dynamic content at edge locations, serving users from nearby servers instead of origin.

# Core Concepts

# How CDNs Work

1. Edge Servers: Servers located near users
2. Caching: Cache content at edge locations
3. Origin Server: Original content source
4. Cache Hit: Content served from edge (fast)
5. Cache Miss: Content fetched from origin (slower)

# CDN Benefits

• Lower Latency: Serve from nearby edge
• Reduced Load: Offload traffic from origin
• Better Performance: Faster content delivery
• DDoS Protection: Distribute attack traffic

# Use Cases

1. Static Assets: Images, CSS, JavaScript
2. Video Streaming: Netflix, YouTube
3. API Responses: Cacheable API responses
4. Global Distribution: Serve users worldwide

# Best Practices

1. Cache Static Content: Images, CSS, JS
2. Set Appropriate TTLs: Balance freshness and performance
3. Purge When Needed: Invalidate cache on updates
4. Monitor Performance: Track cache hit rates

# Quick Reference Summary

CDN: Distribute content to edge servers for low latency and high performance.

Use For: Static assets, video streaming, global distribution.

Key Benefit: Lower latency by serving from nearby edge servers.

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