I spent three weeks building a custom authentication system for my first SaaS. I wrote the password hashing logic, built the session management, handled the password reset flows, and felt proud of the clean code. Six months later, I spent more time fixing auth bugs and updating security patches than I did building actual features for my users.
Most developers fall into this trap because auth feels like a solved problem. We think, "It is just a table with users and a hashed password, I can do this in a weekend." But authentication is not just about logging in. It is about the edge cases that keep you awake at 3 AM.
The Hidden Complexity of Auth
When you build your own system, you start with the happy path. Then the real world hits. You suddenly need to handle:
Session invalidation across multiple devices.
