System designHardsd-g087

Subject RecommendationLevel Senior–Staff~50 minCommon in ML systems · Distributed systems interviewsIndustries Technology

Question

Design a 'frequently bought together' and real-time cart/session recommendation system for a grocery-delivery app. Suggestions must update as items are added to the cart ('you added pasta — add sauce?'), reflect within-session intent, handle 100M products with massive popularity skew, and serve under 100ms as the cart changes.

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.