MyNotes
One notes app with auth, email verification and OTP two factor, built five times over in Node, PHP, Laravel, Django and Flask.
One specification, five stacks. MyNotes is a notes app with registration, email verification, login, OTP two factor authentication, per user note CRUD and a send this note to my email action, implemented five separate times: Express with EJS, plain PHP, Laravel with Blade, Django and Flask. Each build is feature equivalent and backed by MySQL, which is the point, the interesting part is not the app but what each framework makes easy, what it makes awkward, and where the security work has to happen: CSRF handling, safe redirect targets after login, session storage and password hashing all land in noticeably different places.