How to run a local Prefect server

Get started with self-hosting by running Prefect server locally.

The Prefect CLI is the easiest way to start a local instance of Prefect server.

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Start the server

1. Spin up a self-hosted Prefect server instance UI with the prefect server start CLI command in the terminal:

prefect server start

2. Open the URL for the Prefect server UI (http://127.0.0.1:4200 by default) in a browser.

3. Shut down the Prefect server with ctrl + c in the terminal.

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Configure the server

Go to your terminal session and run this command to set the API URL to point to a self-hosted Prefect server instance:

prefect config set PREFECT_API_URL="http://127.0.0.1:4200/api"

You can save the API server address in a Prefect profile. Whenever that profile is active, the API endpoint is at that address. See Profiles and configuration for more information on profiles and configurable Prefect settings.

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Database configuration

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Use SQLite (default)

By default, Prefect uses a SQLite database stored at ~/.prefect/prefect.db. No additional configuration is needed for basic use.

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Use PostgreSQL

To use PostgreSQL as your database backend:

1. Set the database connection URL:

prefect config set PREFECT_SERVER_DATABASE_CONNECTION_URL="postgresql+asyncpg://postgres:yourTopSecretPassword@localhost:5432/prefect"

2. Start the server:

prefect server start

For more database configuration options, see the database settings reference.

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Database management commands

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Reset the database

Clear all data and reapply the schema:

prefect server database reset -y

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Manage migrations

Apply database migrations:

# Upgrade to the latest version
prefect server database upgrade -y

# Downgrade to the previous version
prefect server database downgrade -y -r -1

# Downgrade to a specific revision
prefect server database downgrade -y -r d20618ce678e

On PostgreSQL, migrations use a dedicated statement timeout instead of the general database timeout, and have no timeout by default. For large databases where you want to bound how long a migration can run, set a migration timeout:

export PREFECT_SERVER_DATABASE_MIGRATION_TIMEOUT=600
prefect server database upgrade -y

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Multi-worker API server

For high-throughput scenarios, you can run the server with multiple worker processes to handle concurrent requests more efficiently:

prefect server start --workers 4

This starts 4 worker processes to handle API and UI requests concurrently.

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Requirements for multi-worker mode

Multi-worker mode has specific infrastructure requirements:

1. PostgreSQL database — SQLite is not supported due to database locking issues
2. Redis for messaging, event ordering, and concurrency lease storage — the in-memory defaults do not work across processes

prefect server start --workers validates these requirements at startup. If any required Redis-backed setting is still using its in-memory default, the server exits with an error before starting. See the configuration example below for the full set of required settings.

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Configuration example

# Set PostgreSQL connection
prefect config set PREFECT_SERVER_DATABASE_CONNECTION_URL="postgresql+asyncpg://postgres:password@localhost:5432/prefect"

# Configure Redis-backed messaging, event ordering, and lease storage
prefect config set PREFECT_SERVER_EVENTS_MESSAGING_BROKER="prefect_redis.messaging"
prefect config set PREFECT_SERVER_EVENTS_MESSAGING_CACHE="prefect_redis.messaging"
prefect config set PREFECT_SERVER_EVENTS_CAUSAL_ORDERING="prefect_redis.ordering"
prefect config set PREFECT_SERVER_CONCURRENCY_LEASE_STORAGE="prefect_redis.lease_storage"

# Configure Redis connection
export PREFECT_REDIS_MESSAGING_HOST="redis"
export PREFECT_REDIS_MESSAGING_PORT="6379"
export PREFECT_REDIS_MESSAGING_DB="0"

# Start server with 4 workers
prefect server start --workers 4

For a complete Redis setup including authentication, TLS, and Docket coordination for background services, see How to scale self-hosted Prefect.

The number of workers should typically match the number of CPU cores available to your server process, but you may need to experiment to find the optimal value for your workload.

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Advanced configuration

For advanced deployment scenarios including:

• Running behind a reverse proxy
• Configuring SSL certificates
• Multi-server deployments
• Handling migration issues

See How to scale self-hosted Prefect.