[Yandex Cloud documentation](../../index.md) > [Yandex MPP Analytics for PostgreSQL](../index.md) > FAQ > Working with external tables

# Working with external tables

#### How are user credentials transmitted when working with external tables? {#pxf-users}

When working with [external tables using the PXF protocol](../concepts/external-tables.md), user credentials are provided as plain text. Therefore, such credentials are only available to the administrator user with the `mdb_admin` [role](../concepts/cluster-users.md#mdb_admin). Other users have no access to the credentials for security reasons.