Why Latency Is the Enemy

The speed of light is not negotiable. A server in Frankfurt responding to a user in Sydney will always be slower than a server in Sydney. Every millisecond of physical distance costs you real load time.

A Content Delivery Network solves this by caching your content at dozens or hundreds of locations worldwide — called edge nodes or PoPs (Points of Presence). When a user requests your site, they get served from the nearest node.

What to Put on a CDN

Most teams start with static assets — images, fonts, CSS, and JavaScript. That's correct, but it's only the beginning.

• Static assets — images, fonts, CSS, JS bundles

• HTML pages — especially for static or ISR-rendered sites

• API responses — for cacheable data endpoints

• Video and large files — stream from the edge, not your origin

Modern CDNs like Cloudflare, Fastly, and Vercel Edge Network also support running logic at the edge — authentication, redirects, A/B tests — which moves even more processing closer to the user.

Cache Invalidation

The hardest part of CDN strategy isn't configuration — it's invalidation. How do you ensure users get fresh content after a deploy?

Immutable assets (JS bundles with content hashes like main.a3f9c2.js) can be cached forever. The hash changes when the content changes, so you never need to invalidate.

HTML and dynamic content should use stale-while-revalidate or short TTLs (60–300 seconds). This gives you most of the speed benefit while keeping content reasonably fresh.

On-demand purging via CDN API allows you to invalidate specific URLs or tags on deploy — the most precise approach for critical content.

Cache Hit Rate

A CDN is only as good as its cache hit rate. If 70% of requests still reach your origin, you're not getting the full benefit.

Improve your cache hit rate by normalizing query parameters, grouping similar requests, and avoiding session-specific or user-specific data in cacheable responses.

Choosing a CDN

For most teams, Cloudflare offers the best combination of global coverage, developer tooling, and price. Vercel and Netlify bundle edge CDN behavior automatically for frontend deployments. Fastly is preferred when you need fine-grained control over cache logic.

Start simple: put your static assets on a CDN and measure the difference. Then expand from there.