Was reached out by a recruiter online and passed me some basic screening questions and a technical survey (it asks you to rate your own technical competencies in different areas) to fill out. Once they see that it's a fit, then you will have a phone interview with the hiring manager asking you several technical questions based on the survey you filled out (e.g. if you rate yourself 10 in Java then you should expect questions from Java).
Then they will ask you to do 2 projects. One is more open-ended and another one is troubleshooting related. Start early and don't procrastinate, and learn a bit about Mule platform (use free online tutorials) before starting the project!
Then followed by an on-site interview, consists of technical and behavior questions. Technical questions were asked by the Architects and behavioral were asked by the management. It seems like technical questions may be tailored for each candidate based on candidates previous experience so anything you filled out in the survey or in your resume is a fair game. Note that they will also ask you to perform troubleshooting real-time.
Then followed by a phone interview with their VP/SVP, which asks you behavior questions. Expect why Mulesoft type questions, and prepare some good questions to ask them as well!
Mulesoft takes interviews very seriously so be prepared as well. They might be a bit picky on hiring, but this also filters out the mediocre candidates as well.