Round one was a technical interview with a director of engineering. More of a casual discussion.
Next was a take-home test. This was a little time-consuming (around 30-60 minutes), but was good in that it was easy work typical of what I'd expect the job itself to entail. A matter of building adding simple CRUD endpoints to an existing REST API. As the API already followed a particular structure, it was easy to build onto and didn't pose any real challenge.
After that was reviewed, I had another interview. This time with the director (again) and four engineers. Round-panel discussion focusing on approaches to problems rather than any specific "gotcha" quizzes that companies sometimes resort to, so that was a plus. The conversation flowed well and focused on things I had many years of experience in.
All the interviewers were pleasant and likeable, except for one who seemed a bit standoffish and had an unfriendly demeanor that seemed to indicate he was trying hard to find a reason not to hire me. I'm not sure why. He kept butting in at the end, as the conversation was winding down, to say "wait I have more questions to ask!" Bit of an odd behavior.