Comment by john_strinlai

remember that we already did the "Excellent answer, that is what I would do as well, now what if we wanted to build it in-house?" part.

the "good answer" was already acknowledged, the "real-world scenario" answer was accepted.

the second part ("what if we wanted to build it in-house") is purely hypothetical to gauge how the interviewee would approach the specific technical challenge (shedding some of the "real-world" constraints so that the focus is technical).

if they again say "well that is dumb i would just use sheets", that is absolutely an interviewee problem.