Understanding AWS authentication
The AWS Amplify Framework uses Amazon Cognito as its provider for authentication. Amazon Cognito is a robust user management suite that includes all the latest identity and access management standards, such as OAuth 2.0, SAML 2.0, and OpenID Connect.
Since it's a SaaS solution, you will have a free tier of 50,000 Monthly Active Users (MAUs) to start your next project, until you hit the limit and start paying the paid tier of each additional user that is above the free tier. It can be scaled to millions of users without you trying to figure out a solution to tackle the scalability problem. This is because it is all being handled behind the scenes, which takes all the stress away from all the scalability issues that you might be facing for your potentially super successful product.