When I interviewed for a high level engineering position at Facebook, the questions I got were were definitely harder than the ones some friends of mine got whe

When I interviewed for a high level engineering position at Facebook, the questions I got were were definitely harder than the ones some friends of mine got when interviewing at lower levels. I also had a "System Design Interview" which they did not have. Ironically I failed the System one because I think the interviewer didn't actually understand the algorithms or solutions and was working off a checklist of expected buzzwords. I spent about it 30 minutes working through a design with him putting down all my decisions. Halfway through he tells me I don't seem to be aware of this certain data structure which is necessary, so he'll tell it to me: A quadtree. My original choice was an R-Tree, I tried to tell him it's faster for windowed queries, more accurate when it comes to large locations. The only real downside relative to a quadtree is slower inserts and deletes [0]. He just kept looking at his second monitor and telling me "Well this says a quadtree is the most efficient method". Couldn't tell me why, just that his notes say so. [0] we had discussed at the start of the question, expectations of 1B queries/day, with an acceptable update latency of 24 hours.