Supabase is based on Postgres, basically it provides an API using PostgREST. This means you automatically get a route for each table in your database where you can CRUD entries. To add additional business logic Supabase uses Postgres extensions like plv8 to execute i.e. Javascript. This basically moves your app logic directly into the database. Besides such extensions Supabase also provides a way to define functions which can also contain business logic and can be executed.
With Fusio your API is not build directly on top of your database instead you define an operation where you can freely select a route. If the route is invoked it triggers a specific action. An action is similar to a function at Supabase where your business logic is contained. You can simply create your own action but it is also possible to use our predefined actions solving different tasks like CRUD entries from a database.