Welcome to your interview.
The question is on your right: Learning a Complex Concept Fast. 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.
Tell me about a time you had to learn a complex technical concept very quickly in order to help a customer. What was the concept, how did you get yourself up to speed, and how did you turn that learning into a useful outcome for the customer?