I applied through an employee referral. The process took 2 months. I interviewed at Criteo (Paris) in Jan 2017
Interview
Online 1h test in a programming language of your choice (be sure to really study the theory, there weren't many coding questions, but a lot of syntax & language functionality) followed by a skype interview (which I had accidentally, it's more likely to have an on-site interview).
Interview questions [1]
Question 1
what happens when you click a link on a webpage? (step by step, including processes of the hardware for the mouse click, all the protocols, etc )