Feature flag service
Design a simple feature-flag service for one company's apps. An admin can turn a flag on or off, or enable it for a percentage of users or a specific list of users. The apps check flags on nearly every request, so the check must be fast and must not fail if the flag service is briefly unavailable. Cover the data model, how an app evaluates a flag for a given user, and how you make checks fast and resilient.
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.
Clarify3:30 left
Estimate3:30 planned
Design10:00 planned
Deep dive8:00 planned
Failure5:00 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.