Code Room
System designHard
Question
Design the caching layer for a celebrity-account read path on a social network where a single profile/timeline key can be requested 500k times/second during a viral moment. Reads dominate writes 10000:1, but a profile edit must reflect within a few seconds. You have a Redis fleet in front of a sharded Postgres. Walk through how you keep a single hot key from melting one shard, and how you avoid a cache stampede when that key expires.
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
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Run or narrate your approach, then ask the coach.