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.
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.
Amazon Aurora PostgreSQL parameters
The max_slot_wal_keep_size parameter controls the quantity of WAL data that the RDS for PostgreSQL DB instance retains in the pg_wal directory to serve slots.