Very unprofessional. They have a woman arranging interviews who seems to be in a small closet, shouting into a speakerphone. Hard to understand with all the distortion. She did not send out an interview agenda or any other email to confirm the date/time. You end up with a 22-year-old asking you "Where do you see yourself in 5 years?" and a senior manager asking "Why are you still in technical support?" Some of the people interviewing have only been with the company a short while. Then you receive a curt note saying they are "pursuing other candidates." The whole process was bizarre and insulting.
You don't ask a seasoned, working professional in the telecom industry to take a day off for an interview (out of the blue) and then ask them why they want to work at Twilio. You're supposed to be selling Twilio to the candidate - the interviewers made little effort to do this. My impression is they have no idea what they are doing.