Phase 1: a challenge sent over email. Consisted of 4 questions: basic conversion, UNIX commands, scripting, communication. If you get all four correct, you move on to an on-site interview.
Phase 2: the on-site interview with about 10 people, most of who were PSTs. They all took turns asking me questions. They really focused on the projects I had in my resume (coming from a tech background) and asked many behavioural questions. Make sure you review your resume beforehand and know every technology in your projects! It doesn't hurt to also search up common interview questions :)
The whole process took about a week from when I applied to the on-site. They replied very quickly and allowed me multiple tries at the challenge, which was very generous of them. It took about another week to receive an offer. Unfortunately the PST position closed so they offered me the internship. All in one, a very pleasant experience!