The process took almost 3 months from start to finish.

I was initially contacted by HR for a phone discussion covering standard HR topics.

This was followed by a one-hour technical phone screen. The questions focused on Java and OOP concepts, bitwise operations, and other theoretical topics.

Next, a three-hour onsite interview was scheduled:

• The first hour was dedicated entirely to technical subjects, including multithreading, polymorphism, and debugging provided code.
• The second hour involved two questions:
  • An estimation quiz (e.g., "How many credit cards does Amex approve each year in the US?").
  • An architecture troubleshooting scenario (e.g., "Given an architecture diagram and several production scenarios causing problems, how would you identify the root cause?").
• The final hour consisted of behavioral questions (e.g., "Have you resolved conflict in your previous job? How?").

How many credit cards does Amex issue in a year in the US?