Initial phone screening with HR. They followed up throughout the process and was a pleasure to talk to. 4 hour take home assessment on OOP and a very specific data structure. Followed up by 2 hour call with 2 senior devs who ask questions about design and improvements. They give hints on what problem areas before this so you have time to prepare. Was rejected after this. Overall a very hard and time consuming interview process. HR followed up after to give rejection over the phone, A welcome gesture.