app/code/Magento/MysqlMq/README.md
This module provides message queue implementation based on MySQL.
This module contains a recurring script, declared in Magento\MysqlMq\Setup\Recurring
class. This script is executed by Magento post each schema installation or upgrade
stage and populates the queue table.
This module creates the following tables:
queue - Table storing unique queues.queue_message - Queue messages.queue_message_status - Relation table to keep associations between queues and messages.For information about a module installation, see Enable or disable modules.
For information about significant changes in patch releases, see Release information.
Cron group configuration can be set in the etc/crontab.xml file:
mysqlmq_clean_messages - clean up old messages from database.