Video CDN edge storage

Design the edge storage + caching layer of a video CDN optimized for live and VOD streaming. Constraints: catalog far exceeds any single PoP's disk, segment requests are bursty and follow a heavy-tailed popularity curve, a live event can flash-crowd a single title, eviction must protect popular segments, and you want a high byte-hit ratio while keeping origin egress (the expensive part) low. Cover segment storage at the edge, admission/eviction, and live vs VOD.