The interview consisted of logical thinking test (just a small quiz), two skype screening calls, one technical and one more HR oriented with a manager from the development team and an hour or so pair programming session via cloud9. The screening was oriented on the usual career questions and experience and judging from my experience being sincere about your experience helps. The pair programming session was quite well prepared and tested my Erlang knowledge well, considering the limited time dedicated to the session. After these remote parts of the interview I got invited to Stockholm, where I attended 4 different sessions - architectural, programming, HR and managerial. Architecture interview tested my understanding of the product I work on now, the programming one was half on agile and half on the usual interview programming assignments, the HR on something I don't already quite remember exactly besides my expectations and the like, and the managerial on Klarna, org chart, product description, culture etc. Overall the interview made sense and the people I met there made the imptession this was not their first interview ever. The offer came the very same day I attended the interview, so it seems Klarna is capable of making decisions fast.
Note: I declined the offer due to family reasons.