Hi,
with the graphql Api will we need to have an external server for authentication or notifications ?
Or firebase ?
Realm has in-built authentication (email/pass, anonymous, API Key, etc) but you can also build your own authentication system or use a 3rd party (firebase, cognito, auth0) and authenticate to Realm using a JWT. Both approaches are outlined here - https://docs.mongodb.com/realm/authentication/providers/