It was a two-step process. Step one was an interview with a recruiter over the phone which was fairly easy. Make sure you fit the basic requirements and can handle a job with a lot of cold outreach. The second step was a panel hour-long interview which consisted of a cold call role play, prospecting assignment questions, and traditional interview questions.
The panel interview was interesting, to say the least. I believe it is set up in a way to ask you questions and see how you respond under pressure. You will feel uncomfortable during this phase. I have had other SDR role interviews which were not as intense. Some questions that were asked were way above the understanding of a fresh SDR, but I believe they were asked to see how you would respond under pressure.
I felt great on the role play, terrible during the prospecting assignment portion, and great again during traditional interviews. Ultimately you can't prepare for everything and need to be calm throughout even if you suck on a certain section.