Long hiring process. Applied through the UN careers website in August, convoked to a written test in October, took the 4-hour test in December at UN New York HQ. Found out July of the following year that I had passed the test and was invited to participate in a 1-hour phone interview with 4-5 officers plus HR. The questions were not hard necessarily, they are all common sense questions that you can prepare for by googling competency-based interview questions, but there were a LOT of questions and it was exhausting. Passed the interview and was added to the roster in September.