[billdybas]

I agree. I think their recommendation is a bit overzealous.

I can see the argument if you have a web frontend that consumes data from multiple backend services – have one GraphQL service that manages them all instead of a GraphQL layer on each service.

But this breaks down greatly when you have different "Viewers". In a web app, the "Viewer" can be a logged in user. In an admin dashboard, the "Viewer" is very different – an employee acting on behalf of users. Service to service communication likely doesn't have a concept of a "Viewer".

I would propose that you have different schemas when you have these different views of the world or different permission boundaries. The business logic can be shared – you may just enforce different authorization checks at the GraphQL layer. You could also share GraphQL types that are common between schemas.