Uber System Design Interview: Messenger-Style Chat at Uber Scale

The interviewer opens

Hi, and thanks for joining me today. Welcome to your interview for the software engineer role at Uber. We'll design a system together, and you can sketch on the whiteboard on the right of your screen as you talk. If you need to step out or take a break, the Pause button at the top right will pause the interview at any time.

The problem is a Messenger-style chat service, and it's up in the Problem tab now. Please read through the requirements and ask me anything you'd like clarified before you start drawing.

The problem

Design a chat service like Messenger where users exchange text messages one-to-one and in groups, receive messages sent while they were offline, see delivered and read receipts, and scroll back through their conversation history.

Must do

• Send and receive text messages in one-to-one conversations
• Send and receive text messages in group conversations
• Deliver messages sent while the recipient was offline once they reconnect
• Show delivered and read receipts to the sender
• Load and scroll back through a conversation's message history

Must hold

• No accepted message is ever lost, and each conversation shows messages in a consistent order
• Messages to online recipients feel instant