Extremely long. 7 interviews and a home coding assignment. First contact with HR, then with an engineer. Home assignment (easy one, in Go. Some queue management, not many hours). Review with another engineer, then similar questions as with the first one. Another interview with more engineers, then CTO and finally CEO. All people were nice and friendly during the process. But in the end they reject without reasoning. And if you ask for it, they never answer. After all that time at least a proper answer would be decent.