Welcome to your interview.
The question is on your right: High-Load Sync and Async Processing. 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 do you handle synchronization and asynchronous processing in high-load applications?