As an ex-Googler who's done a fair bit of interviewing, my bar for "will I use this coding question" is to look at the problem statement, do a from-fresh implementation in a suitable language, and if it took me more than 7 minutes, it is not suitable for a 45-minute interview slot (I would expect the candidate to have a solution in ~20 minutes, then maybe 10 minutes of follow-up questions, then flip to "do you have any questions for me").

I thus gave the candidates roughly three times longer than I needed to solve the problem myself, which should pretty much account for the interview situation.