Retention policy cleanup in DBOS is triggered every hour when a RETENTION message is received over a websocket connection from the DBOS conductor.

This event-driven process is initiated externally by the DBOS Conductor service. Upon receiving the RETENTION message, the system executes the cleanup logic using parameters provided in the message, such as cutoff timestamp and row threshold. In the open-source version, users must set up their own cleanup routines, while in DBOS Cloud and Conductor, the process is handled automatically.