First I had an interview with a RH employee by Skype. It was a non-technical interview, I talked in general about my studies and the latest projects I've worked on so far. At one time during the call the RH asked me a kind of a puzzle and I had to think out of loud how to solve it. It's not a problem if you did not succeed to answer that one however try to do your best. A few weeks later I had an interview in the HQ in Dublin. I met 3-4 different interviewers and each asked me to solve a small algorithm problem. You had to explain again out of loud your thoughts. You have a whiteboard to write your pseudo code or real code. You can chose whatever language you want.