Spotify Backend Engineer interview questions

I was excited to be interviewing with Spotify as its a great product and has established itself to be better than competitors. The recruiters were very prompt at reaching out soon after I submitted an application online. I first had call with the recruiter asking about my interests and talking about the position. She set up a skype interview with member from hiring team. The guy was genuinely interested in my past projects and started off by asking some details over resume. He then asked me a coding question, fairly simple string reverse which he then asked to used for sentence reversing. I cleared that interview. Next was onsite interview. There were 4 rounds of 1 hour each with only a minute or two of break. First one focused on behavioral questions. Second one on system design. Third one on big data and machine learning(this was bit of a surprise because recruiter didn't inform me that they were trying to check me on data engineer role too) Fourth one on designing a game and writing code pieces After that I was given tour of the office and ended my interview on a good note.