Content Delivery Networks

Accelerate global content delivery through geographically distributed caching

🌐 What is a Content Delivery Network?

A Content Delivery Network (CDN) is a geographically distributed network of proxy servers and data centers strategically placed around the world to cache and deliver content as close to end-users as possible.

When a user requests content from a website, instead of traveling thousands of miles to reach the origin server, the request is routed to the nearest CDN edge location. This edge server either serves the cached content immediately or fetches it from the origin server, caches it locally, and then delivers it to the user.

CDNs essentially create a global network of distributed caches that bring content closer to users, dramatically reducing the physical distance data must travel and improving the overall user experience across different geographical locations.

🎮 Interactive Visualization

Click anywhere on the world map to see how CDNs reduce latency and improve content delivery

CDN (Content Delivery Network) Visualizer

How to Use:

Click anywhere on the world map to simulate a user request
Watch the first request travel to the Origin Server and get cached
Make another request nearby to see the CDN speed advantage
Compare the performance statistics below

Legend:

🏢 Origin Server

📡 Edge Locations

👤 User Location

Global CDN Network

🏢

Origin Server

US East (Virginia)

📡

London

📡

Tokyo

📡

Sydney

📡

São Paulo

📡

Mumbai

📡

California

📡

Singapore

👆 Click anywhere on the map to simulate a user request

Performance Comparison

Without CDN

0ms Average Latency

Requests: 0

Path: User → Origin Server

With CDN

0ms Average Latency

Requests: 0

Path: User → Edge Location

CDN Benefits

⚡

Reduced Latency

Content served from geographically closer locations

🛡️

Improved Reliability

Multiple edge locations provide redundancy and failover

📊

Reduced Server Load

Origin server handles fewer requests due to caching

💰

Cost Efficiency

Lower bandwidth costs and better resource utilization

🎯 Primary Goals

⚡ Improve Performance by Reducing Latency

The speed of light sets a physical limit on how fast data can travel. CDNs minimize this constraint by reducing the distance between users and content.

Latency Sources:

• Geographic distance (speed of light)

• Network hops and routing

• Server processing time

• DNS resolution delays

Without CDN: User in Tokyo → Server in New York (180ms+ latency)

With CDN: User in Tokyo → Tokyo edge server (5-20ms latency)

🛡️ Increase Availability & Reliability

CDNs provide redundancy and failover capabilities, ensuring content remains accessible even when individual servers or regions experience issues.

Availability Features:

• Multiple edge locations per region

• Automatic failover mechanisms

• Load distribution across servers

• DDoS attack mitigation

Single Origin Server: 99.9% uptime = 8.7 hours downtime/year

CDN Network: 99.99%+ uptime with global redundancy

Additional Performance Benefits

🔄 Reduced Server Load

Origin servers handle fewer requests, improving performance for dynamic content and reducing infrastructure costs.

📊 Better Scalability

Handle traffic spikes and global audiences without proportionally scaling origin infrastructure.

🌍 Global Reach

Deliver consistent performance to users worldwide, regardless of their geographic location.

📦 Content Types and CDN Strategies

🗃️ Static Content (Ideal for CDN)

Static content doesn't change frequently and can be cached for extended periods, making it perfect for CDN acceleration.

📸 Images & Media

• JPG, PNG, WebP images

• Videos (MP4, WebM)

• Audio files

• Cache for: Hours to months

💻 Web Assets

• CSS stylesheets

• JavaScript files

• Fonts (WOFF, TTF)

• Cache for: Days to weeks

📄 Documents

• PDFs and documents

• Software downloads

• Archives (ZIP, TAR)

• Cache for: Days to months

Best Practice: Use versioning or cache-busting for updates (e.g., style.v2.css or style.css?v=123)

⚡ Dynamic Content Acceleration

Even dynamic content that changes frequently can benefit from CDN optimization through various acceleration techniques.

🏃 Edge Computing

• Run code at edge locations

• Lambda@Edge, Cloudflare Workers

• Process requests closer to users

• Personalize content regionally

🔄 Short-Term Caching

• Cache dynamic content for seconds/minutes

• API responses with TTL

• User-specific content with cache keys

• Microcaching for high-traffic pages

🚀 Connection Optimization

• TCP connection reuse

• HTTP/2 and HTTP/3 support

• Gzip/Brotli compression

• Smart routing to origin

Strategy: Use Edge Side Includes (ESI) to cache page fragments while keeping user-specific content dynamic

🎯 Advanced Caching Strategies

🔑 Cache-Control Headers

• max-age: Cache duration

• s-maxage: CDN-specific TTL

• public/private: Cacheability

• no-cache: Force revalidation

🎲 Cache Keys & Variants

• Device type (mobile/desktop)

• Geographic location

• Language preferences

• User authentication status

♻️ Cache Invalidation

• Manual purge/refresh

• Tag-based invalidation

• Surrogate keys

• Time-based expiration

🏗️ CDN Architecture Patterns

Push vs Pull CDNs

📤 Push CDN

• Content uploaded to CDN directly

• Better for infrequently changing content

• Example: Software downloads, marketing assets

📥 Pull CDN (Origin Pull)

• CDN fetches content from origin on demand

• Better for frequently changing content

• Example: News sites, e-commerce catalogs

Multi-Tier Edge Architecture

🏠 Edge Servers

• Closest to end users

• Cache hot content

• Handle majority of requests

🏢 Regional Caches

• Mid-tier caching layer

• Serve less popular content

• Reduce origin server load

🏭 Origin Servers

• Source of truth for content

• Handle cache misses

• Generate dynamic content

☁️ Popular CDN Providers

🏢 Enterprise CDNs

Cloudflare: Global network, security features, edge computing

AWS CloudFront: AWS integration, Lambda@Edge, pay-as-you-go

Fastly: Real-time configuration, VCL scripting, instant purging

KeyCDN: HTTP/2, Brotli compression, affordable pricing

☁️ Cloud Provider CDNs

Google Cloud CDN: GCP integration, HTTP/2, global load balancing

Azure CDN: Microsoft ecosystem, multiple providers, edge locations

Alibaba Cloud CDN: Strong in Asia-Pacific, live streaming support

DigitalOcean Spaces CDN: Simple setup, developer-friendly

🎯 Specialized CDNs

jsDelivr: Free CDN for open source packages and libraries

Bunny CDN: Performance-focused, competitive pricing

StackPath: Security-focused, WAF integration

MaxCDN (now StackPath): WordPress optimization, plugins

💡 CDN Best Practices

•

Optimize Cache Headers: Set appropriate TTL values and use cache-control headers effectively

•

Enable Compression: Use Gzip or Brotli compression for text-based content

•

Implement Cache Versioning: Use file hashing or version numbers for cache busting

•

Monitor Performance: Track cache hit rates, latency, and origin server load

•

Use Multiple CDNs: Implement multi-CDN strategy for redundancy and performance

•

Optimize Images: Use responsive images and modern formats like WebP

•

Implement Security: Use HTTPS, configure proper security headers

•

Plan for Failures: Have origin server fallback and cache warming strategies