System designMediumsd-g088

Subject RelevanceLevel Mid–Senior~45 minCommon in Databases & SQL interviewsIndustries Technology, Software development

Question

Design the query-understanding layer that sits in front of an e-commerce search engine. Before retrieval, it must spell-correct ('blutooth speeker'), expand synonyms ('couch'->'sofa'), detect intent/category ('iphone 15 case' -> Accessories, not Phones), and strip/parse attributes (color, size, brand) from the raw query. Constraints: add under 30ms, handle 30M queries/day, and degrade gracefully when a query is gibberish.

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.