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Real-time gaming leaderboard

Score submissions go straight into a Redis sorted set (ZADD/ZRANGE/ZRANK) for O(log n) ranking; the database only sees a fraction, for durability.

A sorted set doing the actual ranking work, with the database relegated to an async durability path.

• Throughput: 25,000 req/sec
• First to saturate: Nothing at this load
• Estimated cost: $44k/mo

How it works

Leaderboard (Sorted Set)

The whole design lives here: ZADD updates a score and ZRANGE/ZRANK read a rank in O(log n), no scan. Both flows hit it - it is the superposition centre, not a cache in front of a slower store.

Score History

Durability only, and only for writes: a copy of each submission lands here off the hot path so the sorted set can be rebuilt if the cache is lost. Reads never touch it.

Request flows

Submit a score

1. Client
2. Load Balancer
3. Leaderboard Service
4. Leaderboard (Sorted Set)
5. Score History

Read a rank

1. Client
2. Load Balancer
3. Leaderboard Service
4. Leaderboard (Sorted Set)

Other interview practice

• Rate limiter
• Distributed key-value store
• Unique ID generator
• URL shortener
• Web crawler
• Notification system
• News feed system
• Chat system
• Search autocomplete
• Design YouTube (upload + playback)
• Design Google Drive
• Proximity service

Open this architecture in SysPad · All examples