So I won't spend hours remembering it again

You have your VPC stack deployed with exports of:

• ${VPCStackName}-PrivateSubnet1
• ${VPCStackName}-PrivateSubnet2
• ${VPCStackName}-VPCID
• ${VPCStackName}-VPCCIDR

Example of the expected stack could be seen in cloudformation/vpc.yml

Those parameters are used as a primary config of your DB VPC configuration. Currently, it's expecting that you either have your app hosted within that VPC or you manually define a peering connection (e.g. via AWS::EC2::VPCPeeringConnection)

You should have aws-cli installed and logged-in to you AWS account.

Then, you run sh deploy.sh

• Creds rotation;
• More flexibility in setting the RDS params (e.g. engine, capacity);