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

# Prefect server

> Self-host your own Prefect server instance.

After installing Prefect, you have a Python SDK client that can communicate with either [Prefect Cloud](/docs/v3/how-to-guides/cloud/connect-to-cloud.md) or a self-hosted Prefect server, backed by a database and a UI.

Prefect Cloud and self-hosted Prefect server share a common set of capabilities. Prefect Cloud provides the additional features required by organizations such as RBAC, Audit logs, and SSO. See the [Prefect Cloud overview](/docs/v3/how-to-guides/cloud/connect-to-cloud.md) for more information.

> [!WARNING]
>
> We recommend using the same version of `prefect` for the client and server.
> Old clients are compatible with new servers, but new clients can be incompatible with old servers as new fields are added to the REST API.
> The server will typically return a 422 status code if any issues occur.

## The Prefect database

The Prefect database persists data to track the state of your flow runs and related Prefect concepts, including:

* Flow run and task run state
* Run history
* Logs
* Deployments
* Flow and task run concurrency limits
* Storage blocks for flow and task results
* Variables
* Artifacts
* Work pool status
* Events
* Automations

Prefect supports the following databases:

* **SQLite** (default): Recommended for lightweight, single-server deployments. SQLite requires essentially no setup.
* **PostgreSQL**: Best for production use, high availability, and multi-server deployments. Requires PostgreSQL 14.9 or higher. Prefect uses the [`pg_trgm`](https://www.postgresql.org/docs/current/pgtrgm.html) extension, so it must be installed and enabled.

## Database migrations

Prefect uses [Alembic](https://alembic.sqlalchemy.org/en/latest/) to manage database migrations. Alembic is a database migration tool that provides a framework for generating and applying schema changes to a database.

When you start a Prefect server, it automatically runs any necessary migrations. You can also manage migrations manually using the CLI.

## How to guides

* [Self-host via CLI](/docs/v3/how-to-guides/self-hosted/server-cli.md) - Start a local server instance
* [Self-host via Docker](/docs/v3/how-to-guides/self-hosted/server-docker.md) - Run server in containers
* [Scale self-hosted Prefect](/docs/v3/advanced/self-hosted.md) - Deploy multiple server instances for high availability