The interview lasted about 30 min. The agent was super nice, trying to make us feel less nervous and balancing the seriousness of the questions and forms with some funny jokes and comments. He asked us about our story, then some basic personal information and at the end went through the questions on the form I485. He told us he had nothing to be suspicious about and approved us in the spot. I'm getting a conditional green card since we've been married less than 2 years so he explained what he needed to do to renew it and that was it.