I have applied on the careers portal in May.
YOE : 10
Working in a midsize US based product company in Bangalore

Interview process :

1. Hackerrank round : https://leetcode.com/discuss/interview-question/1245302/Booking.com-or-Hacker-rank-test-or-May-2021
   Cleared all testcases except one in final question, booking.com took around two weeks to respond back
2. HR Screening : All about my skills and experience.
3. Onsite coding round : Graph based question on finding Top K closest hotels from a start point.
4. System design : Usecase is about finding bookings made with fraudulent credit cards, the question is same as system design question in https://leetcode.com/discuss/interview-experience/538560/Booking.com-Interview-Experience-(Senior-Software-Engineer)-Feb-25-Reject
5. Cultural fit interview : Lot of LP questions, commercial awareness and how would I test a feature with A/B testing.

The recruiter shared that the feedback is positive after one day. still in negotiations, will share the final offer.
All interviews are taken thru bluejeans.com.

Preparation : 150+ LC and Youtude videos of Gaurav Sen, Tushar Roy, codekarle and System Design Interview.

(update)
Offer :
Base : 90k euros
Perf bonus : 15%
Stock : 20k USD in 3 yrs