Designing a Real-Time Leaderboard

A leaderboard ranks players by score, updating in real-time as scores change.

Requirements

• Update scores in real-time
• Get top 100 players
• Get a player's rank
• Handle 1M+ concurrent users
• Multiple time windows (daily, weekly, all-time)

Why Redis Sorted Sets?

Redis sorted set (ZSET) stores members with scores and maintains sorted order.

ZADD leaderboard 5000 "player:alice"
ZADD leaderboard 3500 "player:bob"
ZADD leaderboard 4200 "player:charlie"

→ Automatically sorted: alice(5000) > charlie(4200) > bob(3500)

Key Operations

# Update score
ZINCRBY leaderboard 500 "player:alice"

# Get top 10
ZREVRANGE leaderboard 0 9 WITHSCORES

# Get player rank (0-indexed)
ZREVRANK leaderboard "player:alice"

# Get players around user (±5)
ZREVRANGEBYSCORE leaderboard +inf -inf LIMIT offset 11

Time-Based Windows

leaderboard:all_time
leaderboard:weekly:2026-W06
leaderboard:daily:2026-02-15

Use TTL to auto-expire old windows.

Persistence

Redis ZSET is primary for rankings; write-through to PostgreSQL for durability.

Sharding for Scale

For 100M+ players, shard by player_id range:

• ZSET 1: players A-F
• ZSET 2: players G-M

Merge top-K from each shard for global leaderboard.

Conclusion

Redis sorted sets are the perfect data structure for leaderboards — O(log N) updates, O(log N + K) top-K retrieval.