Demo case file · System design
Workplace messaging company
Software Engineer II
This is a demo case file: a realistic example written from commonly known interview formats, not a real candidate's interview experience.
Questions asked
- Design a chat service that supports one-to-one conversations and groups of up to 500 members.
- How are messages delivered to offline users, and kept in sync across a phone and a laptop?
- How do you guarantee that messages appear in the same order for everyone in a conversation?
What to expect
They let me pick the depth, but expected persistent connections, a message store and per-conversation sequence numbers. The follow-ups on read receipts and typing indicators were about what doesn't need to be durable.
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