As far as I know you cannot simply host your dedicated Mendix database on an external database service like Amazon RDS if you are running Mendix in the public cloud.
The documentation doesn’t address RDS specifically, but for the example of Microsoft Azure SQL it states:
“For deployments to the Mendix Cloud [...] these settings are managed for you and cannot be overwritten.”
For your case, what would be the motivation to move the DB to RDS? Depending on that, there are different ways to move forward. E.g. if this is motivated by
- the company’s security policy that all data must be hosted in the company’s managed AWS → Move to Mendix for Private Cloud
- the company’s security policy that all data must be hosted in the company’s dedicated (but not managed) AWS → Move to Mendix Cloud Dedicated
- the company’s security policy that all data must be hosted in AWS → Mendix Cloud runs on AWS
- the need to have the data in AWS for data warehousing / other analysis → Develop an API in the app directly or use Mendix backup API to host a replica in RDS
- concerns about the security of the Mendix cloud → find out what the concerns are and if they can be mitigated by Mendix
- the need to profit from a managed database service like RDS like automated backups and patching → Mendix cloud already takes care of that
- directly insert data from other applications to the Mendix database → don’t do that as the Mendix runtime is the only client that should work on that database. Use APIs instead