Masst DocsCDN
Understanding Content Delivery Networks and how they improve performance.
What is a CDN?
A Content Delivery Network (CDN) is a geographically distributed network of servers that delivers content to users from the nearest location, reducing latency and improving load times.
How CDN Works
Without CDN:
User (Tokyo) ──────────────────────► Origin (New York)
~200ms round trip
With CDN:
User (Tokyo) ────► Edge (Tokyo) ────► Origin (New York)
~20ms │
│ Cache hit? Return immediately
▼
User gets contentCDN Architecture
┌─────────────┐
│ Origin │
│ Server │
└──────┬──────┘
│
┌───────────────┼───────────────┐
│ │ │
┌────▼────┐ ┌────▼────┐ ┌────▼────┐
│ Edge │ │ Edge │ │ Edge │
│ (US) │ │ (EU) │ │ (Asia) │
└────┬────┘ └────┬────┘ └────┬────┘
│ │ │
Users Users UsersContent Types
| Type | Examples | Cacheability |
|---|---|---|
| Static | Images, CSS, JS, fonts | High (days/weeks) |
| Semi-dynamic | Product pages, articles | Medium (minutes/hours) |
| Dynamic | User-specific content | Low (not cached) |
CDN Features
Caching Strategies
- Pull: CDN fetches from origin on cache miss
- Push: Origin pushes content to CDN proactively
Cache Invalidation
1. Time-based (TTL expiration)
2. Purge API (immediate invalidation)
3. Versioned URLs (styles.v2.css)Additional Features
- DDoS protection: Absorb attack traffic at edge
- SSL/TLS termination: Handle encryption at edge
- Compression: Gzip/Brotli at edge
- Image optimization: Resize, convert formats
Popular CDNs
| Provider | Strengths |
|---|---|
| Cloudflare | Free tier, security features |
| AWS CloudFront | AWS integration |
| Akamai | Enterprise, largest network |
| Fastly | Real-time purging, edge compute |
Interview Tips
- Know push vs pull CDN models
- Understand cache invalidation strategies
- Discuss edge locations and latency benefits
- Mention CDN for static vs dynamic content