[metabagel]

I don't think someone should have to work for Amazon in order to write a book about how to become a senior developer.

>> "Senior" will vary depending on the size of company and the scale of problems it deals with.

No matter what company you work for, your role is in a specific context, typically within a group or working on a project. And it's not the scale of problems the company deals with which makes you a senior developer. It's the scope of your assignments and the breadth of knowledge and experience which it takes for you to be able to tackle them.

[rmbyrro]

I did not say it's a requirement, just highlighting what type of experience the author has.