System designMediumsd-g134

Subject Proximity searchLevel Mid–Senior~35 minCommon in Distributed systems · Algorithms & data structures interviewsIndustries Technology

Question

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.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.