Learning from interview rejection - What kind of questions should I ask?

Sorry to hear that, I know it must be disappointing :(

Honestly, given that you don't get feedback, I wouldn't get too hung up on this. Interviewing is a numbers game -- the best thing you can do is just to line up a bunch more interviews.

Independent of the feedback from the company, you can also do some self-reflection. You probably know which interviews went well and which didn't. It's worth writing down some reflections after each interview and review questions where you feel like you struggled.

It's interesting that they can't share specific feedback, but the recruiter is also happy to hop on a call. Given that narrow target, here's some questions that come to mind:

1. For future interviews, what can I do to better prepare? - Very generic question trying to get some tactics
2. What were the general areas I could have improved at? - Hopefully they will narrow it down between DSA, system design, and behavioral.
3. What does the dream ideal engineer look like in this team? - Sort of a wacky one
4. Is it possible for us to stay in touch and reconnect in 3-6 months? - Off-topic, but you should try to maintain the relationship and maybe a new role will open up in a quarter or half

As Rahul mentioned, it sucks that you didn't pass but every failure makes you stronger and you'll get it someday. Just keep improving and learning as much as you can. 😊

From my personal experience, sometimes recruiters are willing to share more direct feedback on a call than on an email. I'd definitely use this opportunity and ask specific questions about where you could have done better and where you failed like Alex suggested.

Best of luck!