Company announcements feed
Design the backend for a simple announcements feed inside a company app: an admin posts announcements, and all employees see them newest-first with infinite scroll. There are a few hundred announcements total and a few thousand employees who open the feed throughout the day. It is extremely read-heavy with rare writes. Cover the data model, how the feed is paged, and how you serve the heavy read traffic cheaply.
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.