There was no interview, there were just written personal statements in the application. The only interview component is for the security clearance, which occurs after you already get a conditional offer.
I applied online. I interviewed at U.S. Department of State (Africa) in Aug 2021
Interview
I interviewed for a role designated for family members of FSOs. The interview was held in person with 5 people on the panel: my future immediate supervisor, his supervisor (and deputy of the department), another officer from another department, and a representative from HR. They ask the same questions to every applicant and are not able to waver much from the designated questions (there was no conversation). They asked standard HR questions. The interview lasted 30-40 minutes and I was notified within 10 days that I had gotten the job. Only one round of interviews for this role.
Interview questions [3]
Question 1
"Tell me about a time you disagreed with a team member and how you resolved it"
I applied through a staffing agency. The process took 12 months. I interviewed at U.S. Department of State (Washington, DC) in Jul 2021
Interview
The interview comes after the applicant has passed the written exam. It is quite structured and features one-on-one and group settings. It really depends on who you get as interviewers and how well you gel with the people who are interviewing the same day you are. It isn't easy but I had fun during it.