System designHardsd-g589

Subject Ml ads biddingLevel Senior–Staff~55 minCommon in ML systems interviewsIndustries Technology

Question

Design the ML system behind an ads-targeting and real-time-bidding service that, for each ad opportunity, selects and ranks candidate ads and computes a bid within a 50ms p99 budget at 100k requests/sec. It must predict click and conversion probability, respect per-advertiser budgets and pacing, and run a second-price-style auction. Cover candidate selection, the prediction models, how bids and budgets are managed, and the calibration requirement.

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.