The first step was a short phone discussion with an HR specialist. One of the questions of particular interest was whether I was interested in science since the domain is heavily scientific. I had mostly been working as a software engineer in non-scientific areas, so it was a natural thing to ask. I expressed my true interest in refreshing whatever knowledge I had from the university and in filling the gaps if and when it comes to it.
The second step was a 1-hr long phone session with a software engineer and a manager from the team I was applying to. I was asked to code a trivial algorithm and a test for it, a couple of questions around this task, a couple of general questions (DBs and such), a few questions regarding my CV.
The third step was an on-site interview. I am not German so I had to fly to Munich from abroad and stay in a hotel, the company reimbursed these expenses. The HR specialist who guided me through the process had given me the interview plan beforehand, so I expected this part to take almost half a day. It took that much indeed, but time flew by and I didn't even notice. Also, this plan mentioned an introduction session during which I was asked to tell the team about myself, so I took the trouble to prepare some slides and never regretted: helped me stay on track and have some visible stuff to base on, and maybe even show my presentation skills. After this there was a coding session, the task was to implement a couple of methods of an otherwise ready simple server so that it behaved well for concurrent clients, experiment with it in different ways etc.; then there was a session with the scientific advisor who tested what was remaining of my university maths (not too much). All other sessions didn't really assess my skills but rather were a way for the team (individually and in pairs) to get to know me, and for me to get acquainted with them and to find out more about the processes and the products. And the lunch together that followed the interview felt relaxing :)
I liked the people I met, the family-like atmosphere and the cosy office a lot, all reminded me of some of the labs I had enjoyed working in during my university years, but here with more important challenges and more related to reality. In spite of what I considered to be suboptimal performance from my side in math-related tasks I got an offer soon and accepted it. I then had to complete the process of preparing the documents, applying for the German visa and getting it, which is pretty long in my country, all that for me and my family. The specialists from the HR dept were guiding me through it on a regular basis, my future colleagues in Munich gave me advice about finding an apartment and the next steps after arriving, so my transition went quite smoothly.