I received a call from the hiring manager out of the blue. He conducted an impromptu phone screen, wherein he asked about my technical skills, lab experience, and grades, as well as some more personal questions (i.e. What's the last book you read?). He called back a few hours later to schedule my in-person interview later in the week. The in-person interview consisted of four rounds, each lasting about 30 minutes. Three were with the supervising engineers, one of which was the hiring manager himself. There weren't any real difficult questions, mostly just going over my resume. I was also shown the work area, and taken to meet some of the team members. The final interview was with HR, just basic psychological questions, a quick rundown of pay and benefits. Finally, I was asked to provide a list of references. However, despite being told that they would be in touch (which is admittedly a red flag), I never received any other communication: no calls, no emails, no letters.