Welcome to your interview.
The question is on your right: Backend Algorithm Choice. 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 the specific algorithmic approach you chose for your backend logic and why it is performant.