Booking.com Software Developer interview questions

My friend applied for me as a software developer. I got 4 problems to solve in 75 min on hackerrank it was easy. After that, the recruiter called me that I passed the first phase and asked me why I applied to booking and what I'm expecting and told me that there will be phone interview contain two problems and I will solve it in codepad the idea should be correct and will discuss about the complexity. I passed this interview it was interesting the recruiter called me again and told me about the onsite interview. I get prepared for this step and study system design and solve problems, read in the data structure, She sent to me some useful links to look at. I went to Amsterdam it was a great city to live in it. The interview was 3 phases( algorithms and data structure, system design, culture fit) The algorithm was an easy problem I found the optimal solution for it but will I'm talking they ask me some questions that I didn't know exactly the answer. The system design was good and it was my first time to know about system design. and I failed in the culture fit interview and that was a surprise for me. But it was a great experience and I will apply again when it's available.

After solving code challange, a recruiter calls with you on phone. They ask to you about your experience and expectations. They are giving information about Booking. The critical point is how booking get revenue question. You must know answer of this question.