AWS Cognito User Authentication: An Architecture Deep-Dive
User authentication looks simple from the outside. A sign-up form, a login page, maybe a "Forgot Password" link. Behind that surface sits a sprawling system of token management, federation protocols, MFA enrollment, session lifecycle, Lambda triggers, and security hardening decisions that are expensive to reverse once users are in the system. I have built authentication layers on AWS Cognito for applications ranging from internal tools with fifty users to consumer platforms with hundreds of thousands, and the lessons from those projects inform every recommendation in this article.