Design leaderboard ranking and messenger services
Company: Meta
Role: Software Engineer
Category: System Design
Difficulty: hard
Interview Round: Onsite
##### Question
Design a scalable leaderboard service that supports:
(a) fetching a user’s global rank,
(b) fetching the user’s rank within their friendship circle, and
(c) returning the k users immediately before and after the user in both scopes.
Design a full-featured messenger application supporting real-time chat, message storage, presence, and scalability.
Quick Answer: This question evaluates expertise in large-scale distributed system design, covering competencies in scalable leaderboard and real-time messaging architectures including data modeling, API design, sharding and replication, low-latency read/write paths, ordering and delivery guarantees, presence, and durable storage.