To detect earlier replication lag and avoid user notifications [1]
[1] T3450
The probe is deployed on the monitoring: https://icinga.softwareheritage.org/dashboard#!/monitoring/service/show?host=belvedere.internal.softwareheritage.org&service=Postgresql%20replication%20lag%20%28belvedere%20-%3E%20somerset%29
This task has been migrated to GitLab.