It's impossible to know the one thing that a specific interviewer at Amazon might ask you, as questions vary greatly depending on the role, the interviewer, and the stage of the interview process. However, if you're trying to anticipate a very important aspect of the Amazon interview, it would be the behavioral questions tied to their Leadership Principles. While there isn't a single question they always ask, you can almost guarantee you will be asked multiple "Tell me about a time when..." questions that are designed to assess how you've demonstrated their core values in past situations. Therefore, instead of focusing on "one thing," you should prepare thoroughly for behavioral questions related to Amazon's Leadership Principles using the STAR method (Situation, Task, Action, Result). Be ready to provide specific and detailed examples that showcase your skills and how you align with their culture. A common question you might encounter early on, though not the only important one, is: "Tell me about yourself" or "Why Amazon?" This is your opportunity to make a strong first impression and highlight your relevant skills and interest in the company, potentially tying it to a Leadership Principle that resonates with you.