The interview process is extremely slow. It takes them two months to give me feedback about the onsite interview.

Basically, they don't care about the interviewee's feelings at all.

Besides, it takes me one month to move on to the next step after I finish the OA, and another month to move on to the onsite interview after I finish the phone screen interview.

I have gone through three rounds of interviews, including Data Science questions, System Design questions, and Behavioral questions.

The System Design question was outside my knowledge. The interviewer asked me to design a system for which I have barely any experience.

But the questions were fine; after all, questions are up to the interviewer.