Multi-user to-do backend
Design the backend for a multi-user to-do app. Each user has lists, and each list has tasks with a title, a done flag, an optional due date, and an ordering within the list. Users sign in and only see their own data. The app is used from web and mobile and may go briefly offline. Cover the API and data model, how you scope data to a user, and how you keep task ordering stable.
What a strong answer looks like
Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.
Clarify3:00 left
Estimate3:00 planned
Design8:30 planned
Deep dive6:30 planned
Failure4:00 planned
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.