System designMediumsd-g068

Subject AutocompleteLevel Mid–Senior~40 minCommon in Databases & SQL interviewsIndustries Technology, Software development

Question

Design a search autocomplete service for a maps app that suggests places as the user types. Scale: 500M daily active users, p99 under 60ms per keystroke, a corpus of ~200M places that changes slowly (new businesses, closures), but suggestions must be ranked by the user's current geolocation and recent search history.

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.