# Design a gaming leaderboard: system design interview question

> Frequent score updates, exact global and regional ranks, stable ties, and consistent nearby results during failures.

Source: https://sysround.com/questions/design-gaming-leaderboard
Updated: 2026-11-05


Difficulty: hard. Levels: Mid-level, Senior, Staff+.

## How the interviewer opens it

"Design a service that tracks player scores and standings for an online game. Players can request global, regional, and nearby-player standings. Scores change often, and players expect fast responses."

## What to clarify first

- Population and regions
- Traffic and read mix
- Standings and nearby players
- Score updates
- Ties and membership
- Latency
- Consistency and freshness
- Durability and retention
- Availability during failures
- Deployment and exclusions

## Scope of a strong answer

Core requirements:

- Accept score updates from trusted game servers.
- Return the top players and a player's exact rank for global and regional boards.
- Return players near a player's rank.

Usually out of scope:

- Calculate scores from game actions.
- Detect cheating.
- Support friend standings or past seasons.
- Accept writes in multiple deployment regions.

## What interviewers probe

### Ranks and nearby players

Equal scores need one stable order. Concurrent score updates can make separately fetched ranks and nearby entries contradict each other.

### Score updates across boards

Corrections can reduce scores. A failure can leave one board behind another without violating the response consistency requirement.

### Recovery after data loss

The rank index can lose data after the service records progress. Seven days of events cannot restore scores from the whole season.

### Query load and freshness

One global board defines ranks for every player. More query capacity must not break exact ranks or hide stale results.

## Common mistakes

- The design stores each player's rank and rewrites many ranks after one score update.
- The design uses a score interval to find nearby players, despite uneven score gaps and ties.
- The service keeps only the top players when it must return every player's rank.
- The service ignores duplicate updates, delayed corrections, or revision order.
- The recovery plan cannot restore older acknowledged scores after a zone failure and event expiry.
- The design partitions players before it explains how the service computes exact global ranks.

## The bar by level

- **Mid-level:** Defines ties and nearby results. Selects an index that supports exact rank queries. Handles duplicate requests and defines durable acceptance.
- **Senior:** Makes each response internally consistent. Handles delayed corrections and partial updates across boards. Defines freshness limits and restores acknowledged scores after a zone failure.
- **Staff+:** Validates capacity and recovery time with numbers. Proves recovery remains possible after event expiry. Explains exact ranks across partitions and equal-score concentration.

Practice this question with an AI interviewer: https://sysround.com/practice/new?problem=gaming-leaderboard


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SysRound (https://sysround.com) is an AI practice tool for system design interviews. It has a voice or typed AI interviewer and a shared whiteboard. At the end, you get feedback on each skill and a model answer. The AI feedback can be wrong.