System designHardsd-g612

Subject Cdn video edge storageLevel Senior–Staff~45 minCommon in Storage & CDN · Distributed systems interviewsIndustries Technology, Telecom

Question

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.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.