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Edge cache hierarchies, cache key design, invalidation, origin shield, and edge compute - the system every other system relies on without thinking about it.
Design a content delivery network with hundreds of edge points-of-presence, multi-tiered caching, and edge compute. Customers route traffic through us; we serve cached responses fast from nearby PoPs and forward misses to the origin. We support edge compute - small JavaScript / WASM functions that run at the edge with sub-50ms cold start.
This is the canonical "fast and global" system. Strong candidates anchor on the latency budget (sub-100ms p99 from anywhere on Earth), explain the multi-tier cache hierarchy, and walk through cache invalidation - the second-hardest problem in computer science.
Asking these before diving into a solution is the difference between a "hire" and a "no signal" rating. Pick the questions whose answers would change your design.
Capacity estimation · architecture with all 11 components explained · 6 deep dives · trade-off analysis · 8 common follow-up questions
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Consistent hashing, eviction, replication, and what really happens when a single hot key takes down the cluster.
Encoding ladders, adaptive bitrate, CDN economics, and the difference between live and VOD. Petabyte-scale storage meets millisecond-scale playback.
Reading is the floor. The interview signal is in walking through this live with someone probing follow-ups. Use the AI mock interview to practice talking through requirements, architecture, and trade-offs out loud.
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