Multi-tenant feature flags
Design a multi-tenant feature-flag service used by ~5,000 customer organizations, each running their own apps. Flag evaluations happen in-app at ~500K evals/sec aggregate and must add <1ms latency (no network call on the hot path). Flags support boolean, multivariate, and percentage rollouts keyed on user attributes. Admins toggle flags in a dashboard and expect changes to propagate to running services within a few seconds. Read-heavy: ~1M reads per config write.
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.
Clarify4:30 left
Estimate4:30 planned
Design13:30 planned
Deep dive10:30 planned
Failure7:00 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.