Hasura extends MongoDB's access control capabilities by providing granular permissions at the column and field level across multiple databases through its unified interface, solving the problem of designing a secure API system from scratch. Hasura enables teams to own a set of databases and collections, known as data domains, allowing for fine-grained role-based access control (RBAC) and attribute-based access control (ABAC) across all sources within each domain. 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 automatically creating schemas and API endpoints that let users query data along with its relationships.