Very quick. If you get a recommendation from someone who's already been working for a couple semesters, you don't even need an interview. Be highly enthusiastic and outgoing during the interview if you do get an interview. Most times, you will only hold the audience's attention for a couple minutes when you present so you will have to wow them/grab their attention fast. If you can't do that during a short interview, then that's probably a bad sign. So bring your A-game.