Too Long; Didn't Read
An Introduction to AWS SSO VS Cross-account Role-based IAM Access is a guide to the best practices in AWS. In 2017, it introduced AWS Organization. It has come as a gamechanger for a large number of situations. Using IAM, you can create and manage AWS users and groups, and use permissions to deny their access to AWS resources. This is the turning point. It is the framework that lets you decide who can access what on your account. Mastering this service is the first step in.