Code Room
System designHard
Question
Design the home timeline for a professional-networking feed with 1B users. Most users follow 200-500 connections, but some accounts (companies, influencers) have 20M+ followers. The timeline must be chronological-ish with a relevance re-rank, support sub-300ms load, and reflect a new post within ~30s for active followers.
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.