Amazon Aurora (PostgreSQL) 支援 Read Replica 了：「Announcing Amazon Aurora PostgreSQL Read Replica for Amazon RDS for PostgreSQL」。
馬上想到的用途是量爆增時，如果當初有作 R/W split (讀寫分離) 就可以直接用錢撐住，不過官方給的範例是降低 RDS 轉移到 Aurora 的 downtime，這點就有點微妙...：
You can now create an Amazon Aurora PostgreSQL read replica for an Amazon RDS for PostgreSQL instance, allowing you to continuously replicate to Amazon Aurora PostgreSQL. This helps you minimize downtime when migrating a live workload from Amazon RDS for PostgreSQL to Amazon Aurora PostgreSQL, by keeping the instances in sync until you're ready to move your applications and users to Amazon Aurora PostgreSQL.
所以這次算是陸陸續續把功能補上來，在 Amazon Aurora (MySQL) 有的一般性功能，這邊就跟著先實作...