I've completed all the stages, but the last one didn't go well. The stages were:

• Stage 1: An Online Coding Challenge
• Stage 2: A Recruiter Phone Interview
• Stage 3: A Technical Phone Interview
• Stage 4: Face-to-Face Interview Onsite in Amsterdam (they paid for flight & hotel).

Stage 1: I was provided a link to HackerRank and had one week to complete the test. I had 75 minutes to solve four problems. Be sure to familiarize yourself with how the platform works. Practice algorithms and data structures problems with difficulty ranging from easy to medium.

Stage 2: This was a 20-minute call with a recruiter, featuring routine questions about my motivation and what I know about the company. These are the easiest parts of the interview process, but prepare thoroughly and learn as much as possible about the company.

Stage 3: This interview was conducted over the phone with two Software Developers, using a shared code editor, and lasted for one hour. I was given two questions. Practice thinking aloud and reasoning about time and space complexity before writing code. The final code doesn't necessarily need to compile, but you should explain your reasoning and provide skeleton code.

Stage 4: I traveled to Amsterdam for three days. I had an interview lasting about 4 hours and 30 minutes, speaking with five different people. There were three parts to this stage:

• Step 1: A technical interview (writing code on paper).
• Step 2: A technical interview (system design).
• Step 3: Commercial awareness.

Pros:

• They provide all the necessary information, including what you need to know, where to practice, and what topics will be covered.
• A three-day paid trip to Amsterdam.

Cons:

• I highly doubt the interview process, especially the initial screening. I know many talented people, researchers, and university professors who might not pass the initial screening stages without significant prior preparation on speed, algorithms, data structures, and language-specific libraries.

Classical questions that you can find on HackerRank or other platforms (easy to medium):

• Data structures: heaps, hash tables, binary trees, tries, etc.
• Algorithms: sliding window, sorting, etc.

I would recommend going to booking.com, looking at all the features the website has, and trying to reverse engineer them. All the questions I was asked were related to the booking.com website services, covering both algorithms and system design.