“There’s an IC sitting out there who just had an amazing idea for a new feature/product. What happens?”Sounds like a good question, but the answer doesn't really matter, because it depends on whether the business actually wants to implement the idea. And if they do, it needs to sound like it's coming from an executive, because if it's not, they'll be embarrassed and try to crush the idea. So if the dev really wants the idea to get into product, they should be funneling the idea through their manager or through a product or sales back-channel.
“Tell me about your last major migration. How long did it take and how long did you say it was going to take before you started?”
Bad question, because they always take longer than they expect and always run into problems, and if they don't they were just lucky. You're asking them to either embarrass themselves to you in the interview, or lie. Not going to give them great feels to remember when they think about your candidacy. Maybe ask them about migrations to see how often they do them, but don't lead them to tell you something specific.
“Let’s say I’m the person you hire. 6 months have gone by, what’s different?”
> You’d be surprised how often I ask this question and the answer I get back is something like “you’ll be here and doing the job”
Yeah, because this is a really bad question. It's not their job to make you have an impact. It's your job to make an impact. That's why it's a job. The question should be them asking you what you will do in those 6 months to make a difference.