> ## Documentation Index
> Fetch the complete documentation index at: https://www.propeldata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Federation

> Query data from other databases and data warehouses.

<div />

Federation lets you query data directly from external sources without copying or moving it.

<Frame>
  <img src="https://mintcdn.com/propeldocs/QOy5SmMMP2AzzqCU/images/docs/federation.png?fit=max&auto=format&n=QOy5SmMMP2AzzqCU&q=85&s=2bfc561cbd149af40ad5022884560ebc" alt="Propel Federation" width="835" height="673" data-path="images/docs/federation.png" />
</Frame>

## Benefits

<CardGroup cols={2}>
  <Card title="Unified view of your data" icon="square-1">
    Provides a single, unified view of your data from various sources without complex data integration.
  </Card>

  <Card title="Improved data discovery" icon="square-2">
    Simplifies finding and accessing data across the organization.
  </Card>

  <Card title="Reduced data duplication" icon="square-3">
    Eliminates the need for time-consuming data ingestion by querying data directly from external sources.
  </Card>

  <Card title="Enhanced governance" icon="square-4">
    Extends Propel's data governance and security features to federated data sources.
  </Card>
</CardGroup>

## Key Features

* **Federated querying**: Query data from multiple sources at once, combining data from different databases and data warehouses in a single query.

* **Fine-grained access control**: [Access Policies](/docs/access-policies) enforce row and column-level access controls as well as [multi-tenant JWT tokens](/docs/multi-tenant-jwt-tokens).

* **Logs and observability**: The platform provides tools for tracking data usage across all sources and facilitates easy data discovery.

* **Integration with Propel APIs and Embeddable UI**: Works seamlessly with Propel's [Query APIs](/docs/query-apis) and [Embeddable UI](/docs/embeddable-ui).

## Supported data sources

<CardGroup cols={2}>
  <Card title="ClickHouse" icon="bolt-lightning" href="/docs/federation/clickhouse/overview">
    Query data from self-hosted or ClickHouse Cloud.
  </Card>
</CardGroup>

## Limitations

* Queries are read-only.
* The speed of queries is limited by the speed of the underlying data source.