System designHardsd-g528

Subject Real time systemsLevel Senior–Staff~45 minCommon in ML systems · Distributed systems interviewsIndustries Computer games, Technology, Software development

Question

Design a live, real-time leaderboard for a competitive game with 50M players where scores change constantly (thousands of score updates/sec) and players want to see, in real time: the global top-100, their own exact rank, and the few players just above/below them. Showing your rank among 50M means computing position in a giant sorted set on every update, which is too expensive to do exactly. Hot events spike updates 10x.

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.