There were a few rounds of interviews including a short introductory interview, followed by 4/5 rounds of technical interviews. I did mine over the phone and online. There were different themes to each interview, from front facing UI/UX to low level systems.

There was an initial screening by the HR with background questions followed by three technical phone interviews, then a chat with the CEO. They normally have an onsite interview also, but I never got to that. They care a lot about your passion to help the world :)