Simple, talk with HR, talk with 'manager' of Engineering, talk with Senior level engineer. This was all done remotely, and fast tracked as there were other pending offers. This company seems desperate to hire folks, so make sure to hit them hard for a higher salary.

Three rounds of interview with 1 round on phone, 1 on site and final one on phone. Overall it was not very difficult. The process did change over the course of the last 4 years,