Nothing useful

Amazon is worst place to start or grow your technology career. When things break, all the tools you will be spending long nights to figure out were internally developed. Therefore, there is no benefit of this experience outside Amazon. The only exception are the AWS services you might be exposed to. Due to the internally developed tooling everywhere, you will be working far from any open source or commercial solutions exist on market. Therefore, when you go to your next job, you are like a new college fresher again because you didn’t learn anything useful at Amazon.