← Microsoft Interview Insights
Started with the obvious stuff, a sorted list, some kind of score store, but then you realize you need to answer questions like: how often does it update, is it real-time or periodic, how many users are we talking about.
Start by clarifying functional and non-functional requirements, such as scale, update frequency, and ranking rules. Then propose a high-level architecture with a real-time leaderboard using Redis sorted sets and a persistent store for durability, and discuss trade-offs between consistency, latency, and cost.
Pro tip: Demonstrate awareness of Microsoft's emphasis on scalability and reliability by discussing how to handle hot keys and sharding in Redis, and how to ensure fault tolerance with replication and fallback mechanisms.
Ask questions to understand the expected scale (e.g., millions of users), update frequency (e.g., real-time vs batch), ranking criteria (e.g., score, time), and any constraints like budget or latency.
Outline the main components: an ingestion service to receive score updates, a real-time leaderboard store (e.g., Redis sorted sets), a persistent database for durability, and an API for querying rankings.
Explain how to model the leaderboard using Redis sorted sets with scores as weights, and how to handle ties, pagination, and range queries efficiently.
Discuss sharding strategies for Redis, caching, read replicas, and trade-offs between consistency (e.g., eventual vs strong) and latency. Address hot keys and how to mitigate them.
Describe how to ensure high availability with replication, persistence, and fallback to the database. Mention monitoring, alerting, and handling failures gracefully.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.