We have enabled the on-prem PostgreSQL (Source) to AWS-RDS (Target) replication by following the official guide and which is worked well. Our RDS cluster has multiple replica's and am trying the enable the different replications for each replica and noticed it's failing due to the following error.

 | 2021-12-01T15:53:49.000+00:00Copy2021-12-01 15:53:49 UTC::@:[12142]:
ERROR:  could not register pglogical worker: all background worker slots are already used 
| 2021-12-01 15:53:49 UTC::@:[12142]: 

Do the replication slot in target(RDS) max_replication_slots is set in cluster level? Is that possible to set it in the replica level? Or to enable every replication do we need to add 10 slots? How many Slots we can open in maximum? The current RDS cluster config is given below.

dev=> select name, setting from pg_settings where name in ('wal_level','track_commit_timestamp','max_worker_processes','max_replication_slots','max_wal_senders  ','shared_preload_libraries');
           name           |                setting
 max_replication_slots    | 10
 max_worker_processes     | 10
 shared_preload_libraries | rdsutils,pglogical,pg_stat_statements
 track_commit_timestamp   | off
 wal_level                | logical
(5 rows)


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