Streaming Replication in postgres between EC2 and Amazon RDS

Streaming replication between an EC2-based PostgreSQL database and an Amazon RDS instance is not directly supported. Amazon RDS provides built-in read replica support for databases within the RDS ecosystem only. You cannot create an RDS read replica directly from a PostgreSQL instance running on EC2.

You can use third-party tools like Bucardo or pglogical to set up replication between your PostgreSQL instance on EC2 and an RDS instance. These tools can help you replicate data between the two instances, but please note that this approach may require more manual configuration and maintenance compared to using RDS read replicas.

Answer is correct.

It is not possible and not supported to build a streaming replication from self-managed PostgreSQL with RDS PostgreSQL as standby.