Design Slack-like chat system

Q: Design Slack-like chat system

This question evaluates skills in designing scalable, real-time chat systems, including distributed systems, data modeling, API design, message ordering and consistency, and real-time delivery mechanisms.

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Question

System design: Slack/Discord-like chat

Design the chat subsystem for an app like Slack/Discord.

Product requirements

The product has workspaces . Each workspace contains channels .
Users can join workspaces and view all channels in that workspace.
Users can send plain-text messages in any channel they have access to.
Users can also have 1:1 private chats (DMs) .
Users can scroll back and read the full message history (assume no expiration).
Users should see new messages without refreshing (real-time updates).
Anticipated top feedback: support editing and deleting messages .

What to cover

Core APIs (send message, fetch history, subscribe for real-time, edit/delete)
Data model and storage
Real-time delivery approach
Ordering/consistency expectations
Scaling considerations and key trade-offs

You may assume typical Slack-like scale (many workspaces, many channels, high fanout).

Design Slack-like chat system

Quick Overview

System design: Slack/Discord-like chat

Product requirements

What to cover

Solution

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