TL;DR: very long hiring process with unnecessary rounds, but a pleasant experience in general.
The initial response to my application was very slow (4-6 weeks), probably because of HR people being on summer vacations. First there was a Skype interview with an HR person, then an online programming test on a 3rd-party site, then an on-site interview with two team members. They were helpful and friendly, it was a pleasant experience. Then there was a "manager interview" with the team leader, which was totally pointless in my opinion - it was a general conversation, nothing interesting. The last phase was the assessment week, where I absolutely didn't feel welcomed - teammates were reserved and didn't really care about me (neither about other teammates, TBH), except one coworker who was very helpful and talked to me about the job's pros and cons very honestly. For me the assessment week was a big disappointment in general (for various reasons), but it ended with no offer so I think it was a mutual no from both sides.