Real-estate search with facets
Design the search backend for a real-estate listings site. Users search by map bounding box + filters (price range, beds, baths, property type) and expect live facet counts ('342 homes match'). Scale: 50M active listings, 10M searches/day with heavy weekend spikes, p95 under 250ms, listings update price/status frequently.
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.
Clarify5:00 left
Estimate5:00 planned
Design15:00 planned
Deep dive12:00 planned
Failure8:00 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.