You don't feel that it's appropriate to ask a "Sr or higher" candidate questions such as: "'how many requests per second can we handle given this hardware', 'how much memory do we really need- if we quadrupled it, what would that get us', etc," ?

In addition- do you feel it's reasonable for a "Sr or higher" candidate to lock up (ie- stammer, not be able to come to any sensible conclusion)if one was to be asked a question where they have to use the same tools to answer those questions above when asked a question not in their domain- for example, 'how many pianos tuners are likely to be in this area'?

I'm not arguing in favor of non-domain experience questions like mt fuji or piano tuners- but I can't see hiring a Sr who can't tell give me some Fermi question approximations about how many servers we need.

Maybe I don't know what a Sr is supposed to be capable of doing?