Design a Slack-like real-time messaging system

Company: OpenAI

Role: Software Engineer

Category: System Design

Difficulty: hard

Interview Round: Technical Screen

Quick Answer: This question evaluates a candidate's competency in designing scalable, fault-tolerant real-time messaging systems, including message persistence and delivery semantics for DMs and large channels, multi-device synchronization, ordering guarantees, and operational concerns like partitioning and latency targets.