Creating Gaming Leaderboards Using Redis

Ronny López Technical Lead Backend

Ronny.lopez@socialpoint.es

Leaderboards

• Effective way to show where a user stands within a gamified system

• Absolute leaderboards – incentivize • Relative leaderboards – avoid disengagement of players at

lower end of rankings• Several type of rankings (weekly, monthly, friends, …)

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Requirements

• Add member• Remove member• Update member score• Find member score• Find member rank• Associate data to members (Name, Alliance, etc…)• Get slices of the ranking (for pagination)

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Architecture

Scalable to serve several million active users Performance is a must

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Implementation

• Redis data structure server• Sorted set data structure• Different sorted sets for different kinds of rankings• Redis hash data structure for member associated data• Lua scripting for aggregating in-memory data • (Sorted) Sets operations (union, intersection, etc…)

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Challenges

• Horizontal scaling• It is not possible to shard a dataset with a single huge key like a

very big sorted set• Two-phase commits if you want to execute a transaction among

different data stores

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Summary

• Redis is the right tool for the job, but datasets can not be bigger than memory

• Exceptional performance (more than 8K leaderboard ops per second in a single instance)

• Easy to use and understand technology• Mature and open source

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