Sachin.

Product · high throughput

Contest Leaderboard

Realtime tournament leaderboards on sharded Redis sorted sets. Built for millions of users. Now with a live frontend.

P95

50ms

Load test

3k RPS

GitHub ↗Live ↗

Problem

JAR Premier League needed a leaderboard that stayed correct under write-heavy contest traffic, with fair tie-breaks and cheap top-N reads.

What I built

  • 10-way Redis shard by userId, ZSET scores with timestamp tie-break
  • Hash of original points + cross-shard rank merge
  • Locust load test: P95 50ms at 3000 RPS
  • React frontend: contest switcher, live top-N, rank lookup, score submit

Architecture

Spring Boot → CacheService (RedisTemplate) → Leaderboard:{contest}:shard:{0-9} ZSETs + UserPoints hash. Rank = 1 + count of strictly higher scores across shards.
JavaSpring BootRedisReact