Interviewer had a particular solution in mind that took a different approach from my own. My solution was algorithmically correct but not one that they were familiar with and preferred a non-closed form solution.

Process was: Recruiter screening, Phone Screen, 5 Virtual Onsite. The whole process took a long time. I loved each interviewer, they were really friendly, nice and passionate with their work. The interview questions were unique and on the harder side but well organized.

Recruiter phone interview, a technical screen, then multiple technical interview rounds. I've gone through non-concurrent programming, concurrent programming, algorithms and the design one; didn't make it to the behaviorial and final interviews, The process is well explained, and I have even got feedback afterwards.