Welcome to your interview.
The question is on your right: Thread-Safe LRU Cache Design. 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.
Design a thread-safe, in-memory LRU cache using both a red-black tree and a hash table.