We hire people based on enthusiasm, general intelligence (you can usually tell after a few minutes) and a low level of demonstrated proficiency - we'll ask them to explain a code sample they wrote, or ask for a verbal description of how to solve a problem. We choose the person we like best, and if they don't work out after 2 weeks we fire them.

Hot seat quizzing produces way too many false negatives. We are not google. We can't do 5+ rounds in search of yeoman geniuses. We have to spend time making money. Some companies don't seem to have this inconvenient little problem, but we do.

And besides, most of our hires have come from existing networks where none of this is even necessary. Having an extensive professional network should be a feature of anyone you consider bringing on as founder or employee or contractor.