Infrastructure
Content Delivery Networks
A CDN distributes content to edge servers worldwide, reducing latency by serving users from the nearest location. CDNs are critical for performance at global scale.
- Edge Caching â Content served from locations near users
- DNS Routing â Users directed to nearest edge server
- Offloading â Origin server load reduced by 90%+
CDNs are the invisible infrastructure that makes the internet feel fast.
What Is a CDN?
A CDN is a distributed network of servers that caches and delivers content from edge locations close to users.
DNS-Based Routing
CDNs use DNS to direct users to the nearest edge server.
Push vs Pull CDN
| Strategy | Description | Use Case |
|---|---|---|
| Push | Origin pushes content to edge servers | Large media files, predictable access |
| Pull | Edge servers fetch from origin on first request | Dynamic content, long-tail assets |
| Hybrid | Pull with background refresh | Most modern CDNs |
Cache Strategies
Cache Invalidation
CDN Architecture
CDN Security
| Feature | Description |
|---|---|
| DDoS Protection | Absorbs volumetric attacks at edge |
| WAF | Web Application Firewall at edge |
| TLS Termination | Handles SSL at edge |
| Token Authentication | Signed URLs for private content |
| Bot Management | Identifies and blocks malicious bots |
Practice Exercises
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Design: Design a CDN strategy for a video streaming platform serving 100M users globally. Consider hot content, long-tail videos, and live streaming.
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Cache Invalidation: A news website publishes breaking news that must be globally visible within 30 seconds. Design a cache invalidation strategy using a CDN.
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Analysis: Compare push and pull CDN strategies for an e-commerce site with 10,000 product pages and 500,000 product images.
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Cost: A CDN charges 0.01/10,000 requests. Your site serves 1TB/month with 100M requests. Calculate the monthly CDN cost.
What to Learn Next
-> Proxy and Reverse Proxy Forward proxy, Nginx, HAProxy, and SSL termination.
-> Rate Limiting Token bucket, sliding window, and distributed rate limiting.
-> Load Balancing Distribution algorithms and L4 vs L7 load balancing.
-> Networking Fundamentals TCP/IP, HTTP, DNS, and network latency.
-> Security Patterns Authentication, authorization, encryption, and mTLS.
-> Cost Optimization Cloud cost management and right-sizing.