I have one major piece of advice, if you’re interviewing for a developer job, or really if you’re interviewing for any job.
If you get the sense that the interviewer is dissatisfied with how you did, don’t hesitate to ask what they’re dissatisfied about.
For example: “It feels like I didn’t completely answer your question. Is there anything I could expand on for you?”
Or: “Did my solution to the exercise cover everything you wanted me to cover?”
If they just say yes, but they still seem dissatisfied, well, then there’s nothing you can do.
But I’ve often found that this will bring forward whatever reservations they have, and give you a second crack at them.