Design Real-Time Gaming Leaderboard
Last Updated: December 30, 2025
What is a Real-Time Leaderboard?
A real-time leaderboard is a ranking system that displays participants ordered by their scores and pushes live updates to all viewers as scores change. Unlike traditional leaderboards that refresh periodically, real-time leaderboards show ranking changes within milliseconds of a score update.
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The core challenge is maintaining accurate rankings while simultaneously broadcasting updates to millions of connected viewers. When a participant scores, the system must update the ranking, determine which positions changed, and notify all relevant clients, all within a tight latency budget.
Popular Examples: leaderboards in online games, fitness apps, or platforms like Kaggle competitions.
What makes this problem interesting from a system design perspective is the fan-out challenge.
A single score update might need to reach millions of connected viewers. If 10 updates happen per second and each one affects 8 million viewers watching the top 100, you are looking at 80 million messages per second. That is not a problem you can brute-force with bigger servers.
This system design problem combines several fundamental concepts: efficient ranking data structures, real-time communication, massive fan-out patterns, and consistency challenges under high concurrency.
In this chapter, we will dive into the high-level design of a real-time leaderboard system.
Let’s begin by clarifying the requirements.