Your question is Optimize a Bottlenecked Database Search. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Given a database search that is bottlenecking under huge traffic, identify the flaws and propose optimizations (scaling, sharding, indexing, SQL join optimization).
Asked in the Technical interview stage. Explain how you would diagnose the bottleneck before changing the architecture, then propose an implementation plan. Address correctness, consistency, operational complexity, cost, and rollback strategy. Discuss whether machine learning is appropriate for query optimization or whether deterministic database techniques are preferable.