Content Delivery Network

What is Content Delivery Network?

A content delivery network (CDN) distributes cached copies of web content across geographically dispersed servers to reduce latency and improve load times for users worldwide. CDNs serve static assets (images, JavaScript, CSS) and increasingly dynamic content from edge servers closest to the requesting user. Cloudflare, AWS CloudFront, Fastly, and Akamai operate global CDN networks with hundreds of points of presence spanning every continent.

How does Content Delivery Network work?

When a user requests content, DNS resolves to the nearest CDN edge server rather than the origin. If the edge has a cached copy (cache hit), it responds immediately without contacting the origin. On a cache miss, the edge fetches from origin, serves the response, and caches it for subsequent requests based on cache-control headers.

CDNs implement tiered caching architectures where regional shields aggregate requests before reaching origin, reducing origin load. Cache invalidation occurs through TTL expiration, explicit purge APIs, or cache tags that allow targeted invalidation of related content.

Modern CDNs also provide DDoS protection, WAF rules, image optimization, and edge compute capabilities. They terminate TLS at the edge, reducing handshake latency, and support HTTP/3 with QUIC for improved performance on unreliable networks.

Why does Content Delivery Network matter?

CDNs reduce page load times by 50-70% for globally distributed audiences, directly impacting bounce rates, conversion, and SEO rankings. Google's Core Web Vitals heavily weight loading performance, making CDN usage essential for competitive search visibility. For AI-powered sites serving large model outputs, CDNs cache repeated inference results, reducing compute costs significantly.

Best practices for Content Delivery Network

• Set appropriate cache-control headers with long TTLs for versioned static assets and shorter TTLs for dynamic content
• Use unique filenames or query strings when updating assets to force cache invalidation at edge nodes
• Implement cache tags for surgical purging of related content without full cache flushes
• Monitor cache hit ratios per path to identify frequently-missed content that needs caching strategy adjustments
• Configure custom error pages and stale-while-revalidate behavior to maintain availability during origin outages