After working with my boss at a previous job he's decided to start a contracting firm and I'm in the first handful of people to help get things started. It's been a few months and now we're looking to expand and hire a more junior developer.
I've helped my boss hire knowledgeable senior level people that I was going to work directly with. It was easier to ask hard questions and if they had a correct answer then I could believe they were good for the job. If I ask a senior person hard questions that they don't know the answer to, I start to have a feeling it may not be a good fit.
Trying to come up with questions for a junior level has me second guessing how to receive their answer. If I ask a junior person easier questions and they don't have an answer, is it because I asked a slightly too hard question for a junior? Should they know this answer? If they got it right, did I ask too easy a question? In theory it makes sense to ask them some technical questions but also some "are you capable of learning what you need to know in order to do your job" kind of questions but that's turning out to be hard in practice.
How can I ask the right questions and set my own expectations properly for interviewing a junior candidate?