First they sent a numerical and a verbal reasoning test. They weren't very difficult but you need to be fast. If you did sufficiently well they ask you do a pre-recorded interview consisting of 4 questions about your skills, motivation and general knowledge of the ECB. You get about 2-3 minutes for each question. If you passed this step they invite to a Skype interview. They mainly asked about technical skills and what you know about the specific division you interview for. They were very friendly and helpful during the interview. The most frustrating part of the entire process is that it takes a long time (2 months)