The process had 3 steps: 1) HR, 2) "Light technical", and 3) "More technical".
First of all, the advertisement specifically mentioned that Oura will go through the applications already during the application period as they come so I sent my application early - however it took two months for them to contact me. This already made me feel that I was some sort of backup choice.
In the first step, the HR made it clear that things are quite chaotic at Oura - and for sure it was. I was bounced back and forth between different teams, interviews were cancelled and rescheduled, and at every step Oura promised to get back to me by the end of the week, and every single time this meant that they wrote me on Friday evening that they will reply later.
After the second round, my third and last round interview was changed from health team to cloud team. At this point I specifically asked the HR if I was still interviewed for data science -position or a data engineer -position that had opened. I was ensured that it would be a machine learning focused data science -position. I cleared up my calender, and booked the interview for 23rd of December(!). To my surprise, over 90 % of the interview focused on nginx, asynhronous processes, parallel computation, and cloud architectures. The interviewers had absolutely 0 interest on the models I had built and only asked questions about the technological choices regarding the environment they were run on.
At this point, my 110 % interest in the company and the position had turned into 30 % interest in the company and 5 % interest in the position itself. As a cherry on top of the cake, I was being told that I would receive the final decision before the end of the year. I was approach by the interviewer 17th of January! At this point, I had no idea of what the position was going to be about anyway, so I had already lost my interest.
Not only did this interview process feel misleading and a waste of time for all parties, it was very unfortunate since I believe I would have been a great fit for the R&D teams, and have a great deal to offer for the ML/DL/model development - i.e. the position that I applied for. In the future, if you run out of positions but are interested in an applicant, perhaps consider letting him/her know this and interview him/her only once you have an open position (s)he has applied for, or let him/her know about your change of plans to ease the preparation and allow the applicant to say no.
Regarding the interviewers, I'd say 4 out of 5 were very nice, and only the HR interviewer seemed to have the experience, preparation and skills to handle interviews.
A few tips for the technical interviewers: 1) Have a set of questions ready so that you do not run out of topics to discuss about. 2) The interviewee shouldn't have to lead the discussion to avoid awkward silences. You should lead the show. 3) Do not ask tricky questions just to show off your own skills. 4) Please, give some feedback if the interviewee is on the right track, provide some tips and hints if needed to lead towards the right solution, and for the god's sake, tell the right answer if asked - It feels really awkward to hear that the answer was partially correct but when asked, the interviewer wouldn't give pointers on any things that was missed.