The Three Question Families

1. Why Classification Comes First

"Design an AI-powered shopping experience" and "Design a fraud detection system" sound similar. They are not. They belong to different families entirely: different architectures, different success metrics, and different parts of the answer the interviewer grades most. Answer one using the approach built for the other, and you have made the single most common structural mistake in this interview. It happens fast too, in the first five minutes, before any real design has even begun