will a cdn actually lower your hosting costs?

CDNs reduce origin bandwidth costs — that part is true. What most engineers skip is the one variable that determines how much: cache hit ratio. A 90% cache hit ratio can cut monthly bandwidth costs by roughly 85%, but that math assumes your content is actually cacheable. Static assets cache cleanly. Dynamic, personalized, and transactional content collapses the ratio fast. Before you sign a CDN contract, you need to model your cache hit ratio by asset type, price your current origin egress cost per GB, and run the residual load calculation against the contract cost. This log breaks down the mechanism, the ceiling Netflix demonstrated with Open Connect, and a three-step framework to make the math yours.