I went through 5 interview rounds.
1st round(video call, general web-tech questions, 1 hour) - Interviewer was a senior lead developer who asked questions on almost everything related to web development technologies, few problem solving questions, questions on deployment tools. He was helpful during interview but was in hurry. The interview went good enough.
2nd round(video call, system design, 45 min) - As much as I remember the interviewer asked me to design URL shortener service. It went really well.
3rd round(in office, front-end, 30-45 mins) - The interviewer was a lead full-stack developer(named Bharat). Questions were mostly on ReactJS, not on feature implementations but completely on how it works internally. My answers were in so much depth that it went over interviewer's head and he started interrupting me every 20 sec. Result - The interviewer wasn't impressed and possible ego hurted.
4th round(in office, in-depth system design) - Design a highly utilized, low latency, multi-region URL shortner and explain every system in depth. I designed and explained the entire system so well that it should have been recorded and put as an educational video :D. Though, I had to alter my initial approach as I went into depth and came across bottle-necks. Result - It was phenomenal, but I am not sure if the interviewer was impressed or not, it went over 1 hour mark. Interviewer was genuinely enjoying the discussion and told that this is the most detailed explanation of this question he has ever heard.
5th round(in office, problem solving) - Interviewer was a back-end(Python) developer, probably into data-science. Question was on finding optimal approach for a river crossing bot given list of people weight in random order. Interviewer expected the answer to be in O(n) complexity. The interviewer gave me hints for sorting the array in O(n) complexity for this specific question. Rest of the solution was easy.
Total result - Never heard back, not even feedback.
I don't know what they are expecting from the candidate. Others have pointed out that the company is simply conducting interview without an actual desire to hire. And that is my impression too.