Design a Public High-Scores Leaderboard

To design a global, real-time leaderboard, I would start by clarifying that we need sub-second latency for updates and strict integrity against bots. For the core data structure, Redis Sorted Sets are the industry standard because they automatically maintain order and allow O(log N) insertion and O(1) retrieval of the top K players, which is critical for high-frequency gaming sessions. The system flow would involve the game client sending a signed request to an API Gateway, which validates the user session and checks for basic rate limits. Validated scores are then written to Redis with the player ID as the member and the score as the score value. To handle fraud, we must implement a multi-layer defense. First, server-side logic should verify that the score is physically possible based on game mechanics and historical averages. Second, we can use a sliding window counter to detect rapid-fire submissions indicative of automation. Finally, any score exceeding a certain percentile threshold could be flagged for manual review or temporary suspension until verified. If traffic spikes beyond a single Redis instance's capacity, we would shard the data by region or game mode. This approach ensures low latency while maintaining data integrity, aligning with Google's emphasis on robust, scalable infrastructure.