Welcome to your interview.
The question is on your right: Investigating Fill Rate Drops. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.
You are given a dataset showing a sudden drop in ad inventory fill rates at The Trade Desk. How would you structure your investigation to identify the root cause?