Welcome to your interview.
The question is on your right: SQL Indexing and DAX Nuances. 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.
Explain the difference between indexes storage in SQL Server, how INTERSECT works, and how you would use ROW_NUMBER without an ORDER BY; also compare SUM vs SUMX in DAX and how you would optimize Power BI DirectQuery.