Design a global multi-game leaderboard

Q: Design a global multi-game leaderboard

This question evaluates a candidate's ability to design a scalable, real-time distributed leaderboard service, testing skills in API design, data modeling, ranking algorithms, ingestion and read-path architecture, caching, sharding, consistency-versus-latency trade-offs, idempotency, anti-cheat measures, and disaster recovery.

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Question

Design a Global, Multi‑Game Leaderboard (Ladder) Service

You are designing a global leaderboard platform used by many different games and modes. Each game maintains its own rankings, and player standings should update immediately after a match ends.

Requirements:

Define APIs for:
- Submitting match results (single or batch)
- Fetching leaderboards (global/region/friends/mode/season)
- Fetching a player's current rank
Propose a data model for players, games, matches, ratings, and leaderboards.
Choose a ranking algorithm (e.g., Elo, Glicko‑2, TrueSkill) and explain why.
Detail the write path from result ingestion to rank computation and propagation.
Detail the read path for low‑latency queries.
Propose a caching strategy.
Explain sharding/partitioning by game and region.
Discuss consistency versus latency trade‑offs for worldwide users.
Ensure idempotency for duplicate result submissions.
Outline anti‑cheat/fraud detection measures.
Describe backfill/recalculation flows (e.g., season reset, algorithm change, bans).
Provide fault tolerance and disaster recovery considerations.

Design a global multi-game leaderboard

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Design a Global, Multi‑Game Leaderboard (Ladder) Service

Solution

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