System designHardsd-g738

Subject Ml realtime inferenceLevel Senior–Staff~40 minCommon in ML systems · Distributed systems interviewsIndustries Technology

Question

Design an online-learning system for a news/feed product where user preferences shift within hours (breaking news, trends). The ranking model must incorporate fresh click/engagement feedback on a minutes-scale, not the usual daily batch retrain, while serving ~60k ranking requests/sec at 30ms p99. You need the freshness of near-real-time updates but must guard against the model overreacting to a transient spike or to bot/abuse traffic, and you must be able to roll back a bad online update quickly.

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

Loading whiteboard…

Run or narrate your approach, then ask the coach.