System design interview questionMediumBasic System Component
Design a Gaming Leaderboard
Design a gaming leaderboard: submit scores and fetch top-N ranks fast.
Interview scope
Client → LB/Gateway → App → Cache (hot ranks) + DB (durable scores). No Client → Cache/DB.
Functional requirements
- Submit or update a player’s score.
- Return top-N leaderboard quickly.
- Optional: fetch a player’s own rank.
Scale and quality goals
- Reads of top-N must be very fast.
- Score updates can be frequent during peak events.
- Hot ranking data belongs in cache, not only cold SQL scans.
Capacity assumption
Design for this scale
Assume ~1M score updates/day and ~50M top-N reads/day (~12 RPS write, ~580 RPS read average).
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