# Message queue Galaxy uses a message queue internally for communicating between processes. This is powered by the [Kombu MQ library](https://docs.celeryproject.org/projects/kombu/en/stable/). For example, when reloading the toolbox or locking job execution, the process that handled that particular request will tell all others to also reload, lock jobs, etc. This is configured via the [amqp_internal_connection](https://docs.galaxyproject.org/en/latest/admin/config.html#amqp-internal-connection) option in `galaxy.yml`. For connection examples, see the [Kombu connection documentation](https://docs.celeryproject.org/projects/kombu/en/stable/userguide/connections.html). See the [URL specification](https://docs.celeryproject.org/projects/kombu/en/stable/userguide/connections.html#urls) on that page for more information on configuring different transports. By default, Galaxy will first attempt to use your specified [database_connection](https://docs.galaxyproject.org/en/latest/admin/config.html#database-connection). If that's not specified either, Galaxy will automatically create and use a separate SQLite database located in your /database folder. ## Transports Kombu and Galaxy support a variety of MQ transport/server options. [RabbitMQ](https://www.rabbitmq.com/) via AMQP is the most popular for production deployments. Visit the [Kombu reference index](https://docs.celeryproject.org/projects/kombu/en/latest/reference/index.html) for a complete list of supported transports and their configuration.