Welcome to your interview.
The question is on your right: Cold-Start and Extreme Sparsity. 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 how you would handle extreme data sparsity and cold-start problems for new sellers and buyers on a C2C marketplace like Mercari.