System design interview question
"Design Slack. Workspaces contain channels; channels contain threaded messages. Users are in many workspaces, see unread badges everywhere, and search their full history. 20 million daily users across 5 million workspaces."
multi-tenancy plus persistent searchable history plus per-user unread state. It differs from WhatsApp in three specific ways the candidate must find: (1) history is permanent and searchable, not a delete-on-delivery queue; (2) everything is scoped to a tenant; (3) unread counts are a surprisingly hard per-user-per-channel derived state.
On Practick another engineer interviews you live for 60 minutes on a question from this bank. They have the full interviewer guide beside the call: the answers to your clarifying questions, the numbers to hand out, a ladder of follow-ups and a scoring rubric. You get the model solution once the session settles. It is free: interview someone for an hour and you have earned your own.
Book a free mock interviewAll 132 system design interview questions
System design mock interviews · DSA interview questions · Free mock interview practice · Browse interviewers · Sign in