I have worked at AWS. The key for the interviews are:
1) know your stuff in term of technical knowledge, data structure, algorithm.
2) Culture fit is huge at amazon. Make sure you read Amazon leadership principles and prepare for specific examples from your work experience.
3) Sign up free AWS account and play with the various products/services. Come up with recommendation to improve AWS.
4) Read the book How To Get A Job At Amazon. An excellent guide to help you navigate the interview process.