I was given around a week to build a small food/recipe app, this was in the same email that followed an interview confirmation with them. During the interview which was about an hour long, I demoed what I build and they further gave instructions of new features they wanted me to add on the spot. It was pretty straightforward. There were 2 interviewers in the room, I had time for a little intro at the beginning and maybe 5 minutes for questions at the end.