System design interview question
Design a Distributed Leaderboard and Real-Time Rankings System (like Elo/MMR in Competitive Gaming at Global Scale)
Design a system that maintains real-time player leaderboards and ranking tiers across multiple competitive games and regions, supporting 500M registered players with 50M monthly active users. The system must handle 100K concurrent rank updates per second during peak hours, support sub-second leaderboard queries for top-1000 players globally and top-10K players per region, and maintain consistency between tier assignments and point totals while handling geographic distribution across 6 regions. Key constraints include: players expect their rank to update within 2 seconds of a match completion, leaderboards must be queryable by multiple dimensions (global, regional, by game, by time period), historical rankings must be auditable, and the system should gracefully handle network partitions between regions without losing rank update integrity.
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