I submitted an application online after emailing a researcher at Microsoft about an internship. The application included two reference letters. I went through three rounds of 30-minute interviews talking about my research and the potential intern projects they'll have this summer. The interviewers were all very nice, the conversations were really enjoyable, and there weren't any algorithms/data structures programming questions. Instead, the questions focused on how I would solve different research problems. A recruiter reached out to me with an offer around a week and a half after interviewing.