Design Discord

This lesson designs Discord, a chat platform where people join communities and talk in shared rooms. Sending a message is a small, ordinary write to a database. Delivering it is the hard part, because one message in a large community may have to reach a hundred thousand open connections within a fraction of a second. Most sections below are about that second half.

1. Problem Definition and Scope

We are designing a real-time chat platform organized into communities and channels. A community is called a server in the Discord app and a guild in its code and API