Your auth works — until a thousand people use it at once

The auth bugs that end companies never show up in testing. They show up under concurrent load, when session tokens collide and user A opens user B's dashboard.

One user logs in — works fine. Ten users — still fine. Your login works, your sessions persist, everything looks secure. Then you hit real concurrency and it comes apart: session tokens colliding, JWTs that never actually expire, one customer staring at another customer's data. That isn't a bug. That's a lawsuit — and it lands precisely because auth was the last thing tested, when it should have been the first thing proven.

The trap is that scale failures are invisible at dev-time. Nothing in a single-account walkthrough exercises two sessions fighting over the same state. You have to manufacture the collision before your customers do.

Two checks from this doctrine

Real value, not a teaser — two of the 4 checks in full. The rest are in the one-pager.

Auth that works for one user hasn't been tested — it's been demoed. Prove it at scale before scale proves it for you.