PostgreSQL 13: Don't let slots kill your primary
If max_slot_wal_keep_size is zero, which is the default value, then there’s no limit. I don’t recommend this, because it leads to failures when slots fill the disk.
Supabase CLI config
To illustrate, assume max_wal_size is 1GB and max_slot_wal_keep_size is 5GB. As long as a slot’s WAL file requirement is within 1GB, it’s wal_status remains reserved.
Working with read replicas for Amazon RDS for PostgreSQL
The last two states are seen only when max_slot_wal_keep_size is non-negative. If restart_lsn is NULL, this field is null.