This was probably the worst interview process I have ever experienced, and not because of the questions asked during the interviews, but because of the recruiters.
The interviews themselves weren't overly difficult and seemed reasonable. The interview loop consisted of tasks and questions related to things I might be doing in the position I was applying for, such as React, Python Flask debugging, and SQL systems design. According to the recruiter, I passed all of the interviews and they were pleased with my performance. I don't think I aced them, but apparently it was good enough (I have 3 YOE and applied for a mid level engineering role).
Apparently, the job I was initially applying for got filled while I was interviewing for it. The recruiter had notified me of this inconvenience before I did the 5 hour interview loop, but encouraged me to do the interview anyway and they'd find a new fit for me. Then the SECOND job I was referred to got filled as well, which I did another interview for on top of it.
The recruiter just kept stringing me along and taking days between emails to get back to me. I hung onto this potential offer for over a month before I decided to finally just take one of my other offers.
The recruiter was incredibly slow and overwhelmed, and he should have passed me along to another recruiter instead of just leaving me hanging for weeks and weeks. I believe I may have eventually got an offer from Etsy since I passed their interviews, but the time it took to work something out was insane.