Spectrum interview questions

Interview process is not super formal no leet code questions, mostly technical questions about past experience or the tech stack you are interviewing for. Some behavioral questions too. Two rounds overall

The interview process moves very quickly once it starts. I was initially told it would be 3 rounds of interviews. I did the 3 rounds in less than a week. After that it took them over a week to come back and say they were going to add a 4th interview. I then did that interview as well. After the 4th interview I was told I didn't get the job due to lack of knowledge in a certain area which should have been noted in the other first 3 interviews so overall not a great experience.