I applied online. The process took 4 months. I interviewed at CERN (Genf) in Jun 2019
Interview
Initially you'll have to go through the process of filling in the online application form. It may or may not involve answering some question (text). Have everything required close at hand to submit it when asked.
Second phase is a video recorded interview. They ask 5 or 6 questions and you are recorded through your webcam (in case of a laptop) as you answer them. Can be a bit stressful due to the timer that is obvious and even goes red during the last few seconds. You can review your answers (recordings) after you're done.
The third phase is the in=person interview at CERN, Geneva. The most exciting one. I got the chance to visit CERn and even though it was a day full of interviews, I would still opt to go through it once more.
Interview questions [1]
Question 1
Most of it was mostly interviews based on my CV. One of the interviewers had a test for me. 6 questions. Relatively easy and basic questions on the subject of electronics. During that time though, for me , you could ask me about Ohm's law and I would not be able to tell you. It depends on the person as far as difficulty is concerned. The questions they put forth are not hard. Concentrate on keeping your stress levels low and you'll do well.