First round is with engineering manager. He asked about recent work n challenges i have faced. Second and Third are technical round. Gave one assignment to write better loader logic in react seperately apart from interview

Recruiter contacted me. There were three rounds. First round was of hiring manager, he asked about general software engineering process (sprint, team size, etc.) that I have followed in my career, about my projects, about the hardest problem that I have worked on etc. It went well. Next round was on coding. Interviewer asked a "real world" graph problem, I solved it using disjoint sets, I had to write pseudo code in google doc. Interviewer was satisfied with the solution and he had no other questions, so he ended interview 15 min early. Next round was system design, they asked me to design their bill/invoice upload flow. I had to design it's APIs, storage etc. It went well, there was no counters from interviewer. Even after everything went well, HR messaged me that I am rejected. No feedbacks for any of the rounds, even after asking it explicitly. I also tried connecting with interviewers just for feedback but no response from any of them. Pathetic experience. Also, I had to remind HR multiple times to schedule the rounds. The interview process is not at all proactive.