One of the best interview I had. I didn't got an offer, but the interview process was unique great, and enjoyed it. Their interview process was more meaningful, unlike normal Q&A or MCQ interviews, its focus was especially on, what we have learnt, where we are applying , what are all the possible ways, which solution we suggested as best. For example the questions are. 1) What are the possible ways to find the non pair element in a array. 2) Which one we think would be the best approach with reason. 3) Then Puzzles. Of course they wont expect one correct answer for a question. Just how we think and approach a solution, is their focus. Rather than a interview, I would say I was a great interaction. And I have to say about the project as well. The concept is a good one and has a social impact. I was eager to work on startups like that, better luck next time for me. There are no specific number of rounds. Until the team is satisfied you will have the panel. Hacker rank rounds may be conducted. Got selected or not is second thing, the time spent was worth.