Why do you think you can't ask candidate about what you need in this interview mode? Sure you can. Just don't expect he (let's stick with this pronoun) will kno

Why do you think you can't ask candidate about what you need in this interview mode? Sure you can. Just don't expect he (let's stick with this pronoun) will know very much -- it's not his domain, he didn't work with that. What you get out of hearing the candidate talk about his past project(s) is the knowledge how he approached problems and if he actually completed anything worthwhile, even if it was internals refactoring and there was no thing visible outside.