The hiring process is rather long to enter the Foreign Service. The first step is to submit your application on USAJOBS.gov. If your application is acceptable, you will need to answer essay questions that are reviewed by a panel. If your essay is good enough you will be asked to an interview in Washington, DC. The interview is not a typical interaction. There's not much back and forth. You are asked a questions and notes are taken on your answer. For the technical questions, someone with an engineering or architecture degree will generally do well. Other questions are more related to how you work as a team or react to certain situations; usually dealing with working out differences with colleagues.