Design a team chat system
Company: OpenAI
Role: Software Engineer
Category: System Design
Difficulty: hard
Interview Round: Technical Screen
Design a team chat system similar to Slack.
The system should support:
- One-to-one direct messages
- One-to-many or group conversations (channels or group chats)
- The full message lifecycle: create, persist, deliver, read, and retrieve messages
Discuss the design end to end, including:
- Core functional and non-functional requirements
- APIs and high-level architecture
- Data model for users, conversations, memberships, and messages
- Storage and partitioning strategy
- Indexing strategy for fetching recent messages and conversation history
- Fan-out strategy for message delivery and notifications
- Message ordering guarantees within a conversation
- How to handle stale reads or data staleness across replicas and caches
- Key scalability and reliability tradeoffs
Quick Answer: This question evaluates expertise in large-scale system design and distributed systems, focusing on real-time messaging, data modeling for users and conversations, API design, consistency and availability trade-offs, storage/partitioning, indexing, delivery/fan-out mechanisms, and message ordering guarantees.