I applied online. The process took 2 months. I interviewed at Booking.com (Amsterdam) in Oct 2015
Interview
It was really comfortable. I think, it is the main thing, what I have to say. All interviewers were very polite, patient and etc. I had some problems with language, but it was not a problem. It was really interesting to speak with all interviewers. They told a lot about Booking, about country, about their feelings of Amsterdam and company.
You will find a bootle of water and energy chocolate in the room for interview, cause it (interview) could take more then 4 hours. You will be interviewed by more than 6 people, but it is not as difficult, as it could be. Interviewers make this process really comfortable.
If you have friend in Booking, he will come to show you the office (or it could be your HR). It is possible, that you will receive an answer on the same day.