A CDN (Content Delivery Network) is a geographically distributed network of cache servers — called edge nodes or points of presence (PoPs) — that store copies of video segments and static assets close to where learners are located. When a learner's player requests an HLS segment, the CDN intercepts the request at the nearest PoP and serves it from cache rather than routing the request all the way back to the origin storage in a single data centre; this cuts round-trip latency from hundreds of milliseconds to single digits and removes the origin from the hot path for every learner request. For learning platforms, CDN is essential at any meaningful scale: a single popular course session with thousands of concurrent viewers would saturate origin bandwidth without edge caching. Major CDN providers used with learning video include Cloudfront, Cloudflare, Fastly, and Akamai; most cloud transcoding services output directly to a CDN-backed storage bucket. CDN also provides rudimentary DRM support through signed URLs or tokens that expire after a set period, preventing unauthorised sharing of course URLs. The cost model is egress-based — typically priced per GB of data transferred from edge to learner — so a platform with many learners watching high-bitrate renditions at the top of the ABR ladder can incur significant CDN costs; this is the primary reason to optimise the bitrate ladder and keep unnecessary renditions out of the manifest. Geo-blocking and content localisation routing can also be enforced at the CDN layer.
