This jives with an interview I did with a Google SRE a couple of years ago. He basically took me down a path of increasingly esoteric concepts, until we hit a p

This jives with an interview I did with a Google SRE a couple of years ago. He basically took me down a path of increasingly esoteric concepts, until we hit a point at which I couldn't recall the answer off the top of my head. He asked how I'd implement it; once I reasoned through it (and recalled the bit of information I couldn't remember at first), we quickly moved on to another line of discussion. I assume this was an intentional approach: find an area of knowledge the candidate should understand at a high level, but probably hasn't committed the details of to memory, and see if they can reason it out. You learn significantly more about someone when they're a bit out of their element; does their confidence evaporate, or do they work through it and come up with a reasonable solution?