Domain knowledge is the uncontrollable here. A junior is still probably a junior 3 months in but they are a lot faster for their domain knowledge (codebase, bus

Domain knowledge is the uncontrollable here. A junior is still probably a junior 3 months in but they are a lot faster for their domain knowledge (codebase, business rules etc). Day 1 (I.e. Your proposed interview) there would be little observable difference between various experience levels/quality of engineer since the overhead of domain knowledge will dwarf anything they already have in their head. That is, unless the problem you pick is so isolated that there is no domain knowledge required. In that case you have expensively reproduced fizzbuzz without the mass memorization of code golf style answers.