Aptiv Object Tracking Developer interview questions

The interview process consisted of three rounds, initial phone screen, technical interview and an on-site interview. The initial phone screen was very typical where I was given an overview of the company, the job profile and the interview process. The technical interview consisted of in depth discussion regarding kalman filters and how I had used them in my projects. The on-site interview consisted of about 5 sessions which were technical and behavioral in nature. The technical interviews consisted of white board exercises which included C++ coding and kalman filter related theory. After clearing the on-site interview, they wanted me to go through one more round of interview which was a coding interview on Skype. This was not discussed earlier was very unusual since I had already been on-site at that point. I guess there was someone equally qualified and they were not sure whom to hire. The entire process took 2 months but I guess this was because it was in the middle of the holiday season