I believe that they filter the applications for the first round, based on some basic criteria. After rolling out admits after their first (unofficial) round, they start dishing out interview invites to the second round candidates based on the availability of seats. This is according to a senior of mine, who is an alumnus of a similar program, so I'm guessing that Columbia MFE would follow a similar policy.
Is this year's interview earlier than last year's? I checked the tracker and forums, and feel like most people received interview invite in February last year. So I am wondering if it means we will get the decision earlier than last year as well lol?