Amazon

I can only speak to AWS rather than Amazon as a whole. And one's experience at a company is at least 50% determined by the quality of their direct manager. So YMMV, but in my experience, you will become better at whatever you do.

Amazon Web Services is a hard place to work and is not for everyone. But it does have massive opportunities for those who want to grow.

We do work hard. If you want a strict 9:00-5:00 job that doesn’t involve being on call, then AWS is not the place for you. But if you are an engineer (or manager) who wants to grow; wants to know how to code and own a system handling a significant percent of the world’s internet traffic; and work in an environment where you are surrounded by incredibly smart people who will challenge you beyond what you thought you were capable of, then you should be interviewing at AWS.

It's hard. You will work hard. You will no longer be the smartest person in the room. If you don't learn how to self-pace and say 'no' when necessary, you will burn out rapidly.