I mean, you know that the answer the interviewer was looking for was "use a trie/prefix-tree, want me to implement it", not "that's not my job, ask another team to setup elasticsearch".

If you're going to do coding interviews, you can say "I would use X tool", but you can't _just_ say that, you also have to say "but if I can't, I would write X algorithm, should I write it?"

Also, based on your description, you're suggesting going from entirely client-side, to having a server round-trip, to make it more performant. I could be misunderstanding the full question and context though.