After I applied on their website I got an email the next day about setting up a phone interview with their recruiter. It was more of a conversation about my background, skills and interest in the digital advertising industry and it lasted for aprox. 20-30 min . The recruiter was very friendly and helpful also, answering my questions in the process.
A few days later I got an email+call in order to set up the next phone interview with the Business Operations director from USA office. This second interview lasted about 30-40 min and it was a pleasant conversation with questions about my background, personality, skills, interests and future plans/roles.
Also a few days later I was informed that they'd like to meet me at an on-site interview. Their HR was very helpful, arranging all the travel and accommodation details for my interview (as I'm not from Ireland).
During the on-site interview I met some of the team members. It lasted for about 3h and a half including lunch with the team and it was a really positive experience. Everyone was very friendly, professional, and seemed very interested to get to know me as a person and to learn more about my background, interests and what I could bring to the team. They really emphasize the importance of being a good fit for the role and in my case the whole process got me very excited as it does feel like a great fit. There was also a short test but if you are familiar with the industry and have some knowledge of the main web technologies, it's quite easy.
The next phase was a phone call with a senior manager from Dublin office.