Calendly Senior Software Engineer interview questions

Phone screen with recruiter, followed by interview with hiring manager, then another day to schedule 4 round of interviews - 2 technical, 1 behavioral, & a closing interview with the hiring manager.

1. Phone Screen with Recruiter 2. Zoom interview with manager 3. Take home assignment (4-5 hours) 4. "Super day" interviewing -- about 4 hours of interviews 5. Reference checks 6. Rejection? Calendly was a negative experience for me because they freely took 8-9 hours of my unpaid time, but rejected me and provided me no useful feedback. I completed their take home assignment and I did strongly in all of my interviews. I was given a very strong impression that they would be moving toward an offer. At this stage, most companies extend an offer contingent on successful background + reference checks. Instead, Calendly used a third party reference checking service called crosschq. They required four separate references (which feels like a lot in my experience), and it forces each reference to fill out an in-depth survey about their experience working with you. And it won't clear until it gets responses from all four. So, I had to spend several days following up and politely pestering my busy references to get this wrapped up. After half a week, I got my last reference to submit on the weekend. The following Monday, I received a generic rejection email. I replied asking for feedback, and the recruiter did get back to me and explained they're not really privy to the final discussion so they couldn't provide much more detail other than it seems like something of concern came up and they couldn't proceed. So.... did one of my trusted references actually give me a bad review? That's a problem I need to deal with if so. Was there some weird problem I don't know about on my background check? I also need to know about that. I tried following up with the manager that I interviewed with to see if I could get more feedback, but I never heard back. It just kind of left me nervous about my references and very confused. Seeing as I gave them a full work day of my time free of charge, I would have appreciated the minimum courtesy so I could address it going forward in my job hunt.