Your question is Search Autocomplete Design. 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).
Design a search autocomplete feature (trie-based, scalability and memory/time optimisation)
Asked in the System design stage. Explain how you would build the practical end-to-end system, including prefix retrieval, ranking, memory optimization, serving, updates, and failure handling. Clarify missing scale and product requirements before selecting concrete limits. Discuss how a lightweight ML ranker could improve suggestions without violating the latency budget.