People near me
Design the 'people near me' feature for a social app with 80M daily actives where users move and the app must surface other online users within an adjustable radius (1–50km), refreshed every ~10s, read-heavy with a ~50:1 read/write ratio. How do you index location, scope the search, and bound staleness?
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.
Clarify4:00 left
Estimate4:00 planned
Design11:30 planned
Deep dive9:30 planned
Failure6:00 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.