Short answer: set it on the background services, not just the API. - The pruning of old events is performed by the EventPersister, which runs as part of the background services process. Only the process running background services reads and applies the retention period for deletion. - Use either

PREFECT_SERVER_EVENTS_RETENTION_PERIOD

(preferred, server-scoped) or

PREFECT_EVENTS_RETENTION_PERIOD

(supported alias). Default is 7 days (

P7D

). Where to set it: - Docker Compose: put the env var on the

prefect-services

container (the one running

prefect server services

). Setting it on the API container alone will not trigger pruning. - Kubernetes/systemd/etc.: set it in the environment for the process that runs

prefect server services

. Verify it’s applied (run this in the background services process/container/pod):

prefect config view | grep EVENTS_RETENTION

Helpful docs: - Self-hosted with Docker Compose: Self-hosted Docker Compose - Database maintenance (events retention): Database maintenance - Settings reference: Settings reference - EventPersister service: EventPersister