The interview process has been one of the most streamlined I have seen in the industry. They know the kind of people that they are looking that will fit their culture and work and select accordingly.
I had been trying for Booking.com since a long time because of their almost obsessive focus on data-backed design (not data driven - there is a difference). I got a call from one of their recruiters after having applied on the company website. The interview was a 3 step process for me.
Step 1 - Introductory call
One of their technical recruiters gave me a call informing that I had been shortlisted for the first round. He understood about my background, asked me a few questions about my own aspirations as a mobile app designers, asked about my biases about iOS vs Android vs Web. All of this was just to understand me as a person. He then gave a brief preview about design at Booking.com and then discussed the next steps in the process.
Step 2 - Online task
Even if I was applying as a Mobile App Designer, I was asked to complete a HTML and CSS task which seemed a bit weird. But if you have the basic concepts of CSS box models clear, its not that difficult a task. However, doing all of that in 30 mins means you need to have the syntax on your fingertips. So best advised to go through some CSS documentation. After having completed it, I waited.
I was then sent a mail saying that I had qualified. I was then given a brief about the next round - to analyze the Booking.com app and come up with three suggestions for improvement and how I could measure if they worked or not.
Step 3 - Phone interview
I was interviewed by two mobile app designers with this task. First it was a generic discussion about the two mobile platforms - disadvantages and advantages of each, and the kind of user aspirations attached to each. This is where your past experience of work on either of the two platforms can come handy.
Then I was asked to elaborate on the ideas I had, the problem I was trying to solve with those ideas and how I planned to measure them. They were really focussed on the measurement part, throwing multiple scenarios of the problem at me. I would advise to first listen to them, think and then respond. Some question were definitely grilling but they gave ample time to think about the possible answers. The only right answers are the solutions that can be measured and decided upon.
I was then given a call saying that I had qualified and that they would like to fly me down to Amsterdam for the rest of the interview. They helped me get my Schengen visa sorted and I was in Amsterdam in a month.
Step 4 - The interview
The interview comprised of 3 rounds with multiple designers. All the interviews were completed in the same day.
After the fourth interview, I was told by the recruiter that I had been selected for the role and they wanted to make an offer. After having gone through the multiple aspects of the offer, I accepted it. In two months, I moved to Amsterdam.