https://github.com/munin-monitoring/munin/blob/master/plugins/node.d/postgres_querylength_
This is part of new behavior introduced with the PostgreSQL 13.4 release, as well as the patch releases for 12.8, 11.13 and 10.18, that makes walsender processes to show their latest replication commands in pg_stat_activity.
What are the long-running processes running START_REPLICATION queries on my Heroku Postgres database? - Heroku Help
AND backend_type != 'walsender'
