Your question is Scalable Notification System. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
How would you design a notification system that is both scalable and performant?
Discuss the end-to-end ML and serving architecture, including event ingestion, notification candidate generation, ranking, delivery, deduplication, and user controls. Explain how you would separate batch and online work, meet latency and availability goals, evaluate notification quality, and detect feature drift, training-serving skew, and delivery failures. State assumptions clearly and justify major tradeoffs.