At least two rounds of interviews -- didn't advance past that. The first interview was a short conversation with the division's Senior Director of Web Development. The second interview was 3.5 hours; first a coding test, then an interview for the specific position, and then a social-type interview. The last half hour was a discussion with the SVP for software engineering.
Originally, the second interview was advertised as 3 parts in 3 hours. I was not expecting to speak with the SVP at the end, while hungry and tired. It would have been nice to have some notice; I probably would have paced myself differently. If you're interviewing with Xometry remotely, make yourself some nice food or high-value snacks to look forward to or eat quickly on a break.