Welcome to your interview.
The question is on your right: Caching and Queueing at Scale. 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.
How would you use caching and message queues in a high-throughput system? Walk through when you would use an in-memory cache versus a queue, and how you would handle ordering, retries, duplicate messages, and backpressure.