I had several thirty minute interviews a number of years ago. Some of the interviews were with two people at once and others were one on one. The questions were pretty standard.

Intervied on campus with an awesome recruiter who I absolutely loved. Very basic interview questions. Invited to an onsite super day (but was far shorter than others I had been to). When we first arrived, had lunch with a current MA, then had a brief presentation on the company and service (which they care about highly). I recommend asking questions to show you're engaged. Next you will either go into your 1-1 with a manager and a 2-1 with more seasoned employees. Next you have a tour and see the awesome terrace! Overall a great day. Decided not to take the job because of the salary, although they offered me the top of the range listed here.

One phone interview. Followed by an in person interview where I met with 4 people. An employee referred me after I submitted my application. They allow the in person interview to be over skype if not based in DC.