Hasura extends MongoDB's access control capabilities by providing granular permissions at the column and field level across multiple databases through its unified interface. This enables organizations to enforce powerful access control rules, join data from multiple sources, and expose it to users via a single API. Hasura makes it possible for teams to own specific databases and collections, also known as data domains, which allows for fine-grained role-based access control and attribute-based access control across all sources. Additionally, Hasura provides a powerful, declarative way to define access control rules at the collection and field level, simplifying the retrieval of related data across multiple databases. By serving as a federated data layer on MongoDB and external data, Hasura enables granular access control through a combination of role-based permissions, attribute-based restrictions, and the ability to join data and apply access across sources.