Note that when you create a Read Replica for the RDS PostgreSQL instance, its the native logical replication which comes into play. Meaning, the disadvantages of having a RDS Read Replica will stay even if you use Aurora PostgreSQL as a Read Replica.
But there are a couple of things which you might want to make a note of:
- Evaluate if having an Aurora Read Replica for RDS PostgreSQL is making sense in terms of using Aurora features and if the price is justifiable to the business
- There might be occasions when you might have to run Aurora PostgreSQL read replica to a different PostgreSQL version than its Primary i.e. RDS PostgreSQL instance as the Major upgrades might not be released on the same date
Answering my own question; When Aurora is in read-replica mode for RDS, no furher reader instances can be added: "Creation of an Aurora Replica in a cluster which is already replicating from an RDS for PostgreSQL master is not allowed."
I guess full Aurora migration is needed by promoting the Aurora cluster and only after that, read replicas can be added.
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