SuperTokens is described as 'Open source user authentication solution. Using SuperTokens, developers can add secure, hassle free auth to their mobile application or website in less than a day. It n alternative to Auth0, Firebase Auth and AWS Cognito' and is an app in the security & privacy category. There are more than 10 alternatives to SuperTokens for a variety of platforms, including Web-based, SaaS, Self-Hosted, Windows and Linux apps. The best SuperTokens alternative is Supabase, which is both free and Open Source. Other great apps like SuperTokens are Keycloak, Firebase, AuthKit and Hanko.
fastify is rest api framework, not an authentication provider