A method for using unified identities in a multi-tenant architecture system is discussed. The method includes receiving a request, at a first service provider, to provide a service for a user. The method includes accessing a representation of a second service provider in a first hierarchical data structure managed by the first service provider. The method includes determining that user data required for the service is managed by the second service provider that manages user identity of the user. The method includes determining that the representation is linked with a full identity reference for the second service provider in a second hierarchical data structure managed by the second service provider. The method includes accessing the user data at the second hierarchical data structure using the full identity reference. The method includes accessing the service via the lightweight identity reference and using the user data at the first service provider.