Note that this is the same interview process for Junior, Middle, and Senior positions. They will choose based on your performance. The bar is fairly low for the Junior and Middle positions. Basic Linux knowledge in the technical aspect is enough; they expect training to teach you what you need. I got the Middle position. Check out the questions for more details.
The process is 100% remote. There are 2 stages (considering I didn't apply, but was referred instead). After the first interview, two days passed before the second one, and 2 days after that they sent the offer.
Stage one is with your direct manager once you're in the company (Team Lead); it takes 1 hour and is the most important one. He'll decide if they want you or not during this call.
The first 30 minutes were spent telling me about the company, hiring model (contractor), working at Plesk (training, workflow, and promotions).
Next 10 saw a quick overview of my work experience and resume, along with a few work and customer service related questions.
Finally, specific technical questions about Linux administration, and yes or no questions to see if you know specific technologies.
Stage two took a little under 30 minutes, and is with 2 people; the Director and the VP of Support. This call is a formality, and will only be offered if they already know they want you in the company. They can stop the recruitment process if they see a red flag at this point; otherwise, you're good to go. They are general HR and customer service questions, nothing technical.