Two interview rounds. The first interview was more about getting know each other, interests, the team. The second interview was with more senior staff members, a bit more on talking about technical abilities and interests, followed by a case study writing assignment. The assignment took 2.5h and was adequate for the level that I applied for.
The process took a long time. Sometimes I did not hear anything for several weeks and had to chase them, other times they were super responsive and called me spontaneously to discuss expectations. Overall positive and friendly, but at times inconsistent!