The most unprofessional interview I have ever had, and I was an ex-GS employee reapplying for a role post completion of my Masters. The interviewers asked highly irrelevant questions which was none of their concern regarding my education abroad and why I was looking to come back to India and if I had studied abroad was that not zero ROI on my investment on the degree - which in my opinion is not their concern. The first round was with a much more senior member who had no questions in particular and I had cleared it in no time. The second round of interviews I had was utter nonsense cause I was not questioned on my qualifications nor my professional experience but rather nit picked on for my interest of pursuing my Masters abroad. The interviewers were highly unprofessional and childish to question me regarding the validity of my dissertation (which mind you received an A3) and went so far as to say my efforts were wasted on my dissertation and that it did not make sense. Honestly was so shocked by how horribly the interview had gone and by the sort of talent they have when it comes to interviewers cause I myself have sat in for interviews of people when I was with GS and this was by far the most unprofessional one yet.

7+ rounds - with 2 different people in each round, motivational / competency questions + some market related and technical questions. varies by role but you need to really understand "Why GS"