This was for the 1st 1 hour tech screen out of 2 (they cancelled the second tech screen because I failed this first one). The question was: design a data structure to implement an autocomplete service that returns the top-k most frequently searched keywords with a given prefix. It needs to support 2 operations: 1. serach(keyword): add a user searched keyword and update your underlying data structure and 2. auto_complete(prefix): return top-k most frequently searched keywords with a given prefix. I had to write this code in a google doc. In terms of the interview experience, I knew that this question required a trie, but I couldn't remember exactly how to implement it best and use it for this specific problem, so I tried to go down a more brute force approach. The interviewer told me to find a more efficient solution. I was completely stuck and received no help or guidance from the interviewer, so I just sat there for 45 minutes, repeating the question to myself.