I submitted my resume to a hiring manager, then he called me one day to proceed phone interview right after he asked me available for talking or not. Phone interview went through my resume around 30 min. Then I went to on-site interview after couple weeks. The interview was scheduled a 45min talk for my research, and meeting with different engineers. Each session takes around 45 min. The first engineer introduced the job description in details and kept asking me "are you ok with 24/7 on-call job". I said absolutely every time but I dont know why he kept asking me. The hiring manager didnt join the seminar, then he asked about my research in his session. He didnt spend too much time on research, and he asked me questions. He asked something from the textbook which I know where to find but I dont memorize. He asked how this thing related to my research. I told him my research is not involved this so I dont have an answer right now but it will be interesting if studying the relation. Then he asked me to think right now. I was stuck because I only remember the concept but not the details. Otherwise I was asked behavior questions as usual.