I was referred by an employee. I was interviewed twice at the same day, one with HR, other with the actual team I was hired for. HR asks regular questions, nothing special. The project I was hired for was on Debian, so they asked me a little about linux. Not much, only to see if I can survive without bothering colleagues when installing a package etc. We also talked about my life, how I decided to become a software developer. There were some simple algorithmic questions as well, but they didn't want me to code, they just wanted to see my approaches. The people were fun, the process wasn't stressful at all.