Applied for Principal .NET Engineer role which later turned out to be changed to "Senior .NET Engineer". I have gone through 7 calls with company. After two "final stages" with two different hiring managers I got rejected, as explained due to inefficiencies in prototype (few steps back in the process). Process took almost 2 months. For leadership: if you don't want to hire based on prototype - say that immediately after prototype review and don't waste candidates time.