What about engineers straight out of college? Or is that too junior?

Also, re: how to interview junior people. I'd say the one thing they don't have is experience, or to measure a senior engineer's abilities it makes sense to ask how many times have you built this <insert rocket ship> before, and what did you learn?

For a junior engineer, it is enough to test for willingness to learn, and aptitude for problem solving. Personally, I hate brain teasers and straight up algorithmic complexity type questions. But, given a real world system, asking them how they would build it is usually a good start. So, test for ability to understand big problems, break them down into smaller problems and then figure out a way to attack each small problem.

Curious about other people's interviewing ideas.