Synchronizing a RDS instance with another RDS instance
DISCLAIMER : I haven't tried this myself

What you asking for is somewhat rare. Nevertheless, it is possible.

Here is a link to Looker.com to explain how.

Basically, you do the following:


Create a read replica
Create a Custom DB Parameter group
Tweak the read_only setting in the Custom DB Parameter Group
When replica has been created, ...


you modify the instance
set Parameter Group to the Custom DB Parameter Group



Once you have the accessibility, you can create the DBs directly in the Slave.

I would normally say "Give it a Try !!!" but I never did this before. So, try it out and tell us all if it worked.