We currently have two EC2 instances and a RDS instance. Both a EC2 instance and the RDS instance a hosted on AWS in the same region. However, the second EC2 instance is on a different region.
Currently we have limited access to the RDS instance to only allow connections from the first EC2 instance using Amazon's VPC and security groups.
We need to allow the second EC2 instance to access the RDS database but currently cross region support for security groups/VPCs are not support. So it looks as though we need to open the RDS instance up to the public internet (looks as though we can limit it to the second EC2's IP address though).
What are the security concerns about doing this? It is running MySQL 5.6.27. It has a strong password associated with it's access (but I don't know if this is sufficient). I can provide more configure details if needed.