CDN
A CDN (Content Delivery Network) is a network of edge nodes spread across the globe that serves static content — images, video, scripts — and even dynamic requests from locations near the user, reducing latency, offloading origin servers, and improving availability.
How it works
The core mechanics are proximity and cache reuse: DNS steering sends each user to the nearest edge node, which serves from cache on a hit and fetches from the origin on a miss, storing the result per its cache rules. CDNs accelerate more than static files — with the right cache rules and edge compute, API responses, HTML pages, and computed requests can all be handled at the edge. The governance points that matter are cache rules: Cache Key design decides which users and paths share cache, origin-fetch policy decides what happens on a miss, and the Purge API refreshes content after deployments. Symptoms of poor governance are low hit ratios (cacheable content missing the cache) or stale updates (uncacheable content cached too long) — our articles on CDN cache hit ratios and 503 troubleshooting cover the debugging paths.
Examples
- 1.Users worldwide load images and video from nearby nodes, making first paint feel local
- 2.Traffic spikes during a sale get absorbed at the edge while the origin stays flat
- 3.Calling the Purge API after a release refreshes edge caches within minutes