The interview process takes 4 stages. In the first interview, they explained the position, the main product of the company (the core is image processing) and went through resume asking questions regarding some of the activities listed.
The second interview is a technical interview were they asked questions about C++, basically going through a code review and assessing performance, time complexity and how to improve the code. The code included some OpenMP routines, and some questions were very specific like what kind of error is generated if something changes. Discuss about edge cases. Data structures in use. The underlying data structure of C++ STL containers and estimations of runtime of operations on them.
Third round is focused on python, testing and validation and the fourth round a meeting with the team to have an open discussion about projects and experience.
Questions require fundamental understanding of C++ and compiler behavior, questions may be tricky so make sure to tackle the questions in many different ways to showcase your knowledge of the language and good practices.