#cdn

You pay for a gigabit connection and video calls still glitch, pages still hang, and games still lag. The number on your bill measures bandwidth, but the thing you feel is latency, and more Mbps does almost nothing to fix it.

Caching is the oldest trick in computing: store an expensive result once, hand it back cheaply forever after. It lives in your CPU, your browser, the CDN, and your database. Here is how it works and when it quietly becomes a liability.

A CDN puts copies of your content on servers near your users so the bytes travel a short distance instead of crossing an ocean every request. The thing most people miss: the bottleneck usually isn't bandwidth, it's latency, and latency is bounded by the speed of light.