MAPE is undefined on most of your data. Pick a metric
Test selectionMediumProblem. Your pipeline reports MAPE by category. For the long tail, where most item-days have zero sales, the number comes back as either infinity or a suspiciously clean figure. What is happening, and what should you use instead?
Before you reveal: say your answer out loud, as if you were in the real interview — get your reasoning across clearly first. There is no single correct answer: reading what the interviewer is really after and defending your own thinking is what makes an answer strong.