I applied through the common online application portal for interns. The website clearly stated that Spotify would get back to me only in January or so. Nevertheless, I could only assume how many interview rounds the process involved and what the different interviews deal with. Probably, this is different for each specific role/internship.
The following process had two interview rounds. The first was technical, the second more behavioural. Each should have lasted for 30 minutes.
Once I received the invitation for the first interview, I was already assigned to a team. The interview was led by two engineers from this team and dealt with technical topics. At the beginning, we dealt with some tech trivia. Then, we continued and did some live coding. The interview lasted a few minutes longer than the initially scheduled 30 minutes.
At the end of the first interview, the engineers were not quite sure about how the process continues. They thought that someone would get back to me quite soon and that this would already be the final decision. However, the reply of Spotify took a week longer and consisted of the invitation to another interview.
The second interview was a behavioural and tech knowledge was not that important anymore. The interviewer was the manager of the team I was assigned to. The idea might have been to know whether the manager thinks that my person fits in the team or not. Nevertheless, the manager talked about the own career, the team and the team's responsibilities. Afterwards, I had the opportunity to ask questions. I asked some deeper questions and we talked about them quite a lot.
During the second interview, I had a good feeling. It felt like the manager was trying to advertise the job to me (successfully). However, towards the end, the manager pointed out that they interview several other candidates who also do not seem to be bad. I again was told to expect a reply quite soon. This time, the interview overrun significantly which was okay because we talked about the available interview time at the start of the interview (a shorter interview would have been possible). The style of the interview might depend very much on the team and the interviewer; take the interview as an opportunity to figure out whether the team is a match.
After the first interview, I could assume a little bit whether my performance was acceptable or not. Even though I had a good impression during the second interview, I had no idea on how the result could be like.
I received the actual positive reply the next week (later than expected) with a very nice HR call where I already got to know about some of the logistical job details. Additionally, I could also ask any question.