4 Rounds in the process. Started with an HR screening. Then I met the hiring manager to discuss the role. Then two technical rounds which were fairly standard. Mostly database and backend style problems

First step was a brief chat with their recruiting agent, which in the end asked me to code a very simple challenge. Second step was an interview with a dev and their VP of engineering. They also asked me to code a small challenge with them, afterwards they asked questions and for me to expand and modify a few features. The last step was a "work day" with their team, which in reality was just another code challenge (using their APIs and such) but this time they added me to their Slack channel so I could ask them for assistance should I need it. After I presented the solution to 4 devs and answered a few questions. The very next day I receive a pretty standard rejection e-mail, which is fine, with no real feedback. When I asked if more detailed was available I received no answer, which I find pretty rude considering I took a full 8hr day to work on their challenge.