Assuming technical competency is given, I think senior engineer really needs to do two things well:
1. Be able to make a design decision - among multiple options and with incomplete data and uncertainties, a senior engineer needs to be able to make a decision and be accountable for it in order to move the project forward. I think a good interview question would be to ask about their difficult design decisions.
2. Be able to identify wrong solution (most of the time) - maybe this comes with technical competency but a lot of resource is wasted chasing solutions that with the benefit of experience, should have been evident early on.
1. Be able to make a design decision - among multiple options and with incomplete data and uncertainties, a senior engineer needs to be able to make a decision and be accountable for it in order to move the project forward. I think a good interview question would be to ask about their difficult design decisions.
2. Be able to identify wrong solution (most of the time) - maybe this comes with technical competency but a lot of resource is wasted chasing solutions that with the benefit of experience, should have been evident early on.