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Matchmaking System Design
Visual Problem Diagram
Scenario
Ranked queue at prime time waits 4 minutes with 200K players online—ELO buckets must avoid smurf stomps while keeping < 60 s match time. The interview is skill rating, queue partitioning, and party size constraints, not game lore.
Design a matchmaking service that groups players into fair matches based on skill, region, and party size within wait-time targets. This is a queue + widening search problem with constraint satisfaction.
You should support join queue, MMR update, party play, server assignment, and penalties for dodge. Be ready to explain bucket widening and regional ping limits.
Constraints
Join queue, skill rating update, party support, match found notification, game server assign
< 60 s match p95 for ranked, fair teams, 99.9% queue availability
10M concurrent online, 1M in queue peak, multiple game modes and regions
Stages ahead
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