I applied for the position in Sofia. The interview took 3 phases:
1) 30 min interview with the Sofia Technical manager - standard question about experience, why wanting to leave current employer, Q&A, basic Java questions
2) Another day - 3 h online task in my leisure time to implement an interface and provide REST endpoints to its actions
3) Another day - 2,5 h live interview with 5 members of the company. Asked questions about SQL(selecting, grouping, table optimization), Java, Data Integration patterns, Elasticsearch(due to my experience). Java concurrency, Stream API, lambdas and latest (version >=8) Java features seam to be a must for the job. Also given a simple coding task. Discussed "better" or missing functionality of the service developed in the previous day.
As a whole the interview was a positive outcome for me. The only drawback is the online coding platforms bugs and not the best sound experience. I have doubts that I have had a good understanding of some of the questions. Had to ask the guys to repeat the questions and was really annoying for both sides.