I see a lot of articles online where EC2 is involved, but since my backend is essentially serverless I have not found much information how to access my RDS once it is turned private. Can anyone point me in the right direction?
Current state:
Future state:
In your scenario your Lambda functions will need to be configured to run in the VPC if they are not already. That is the only change required for the Lambda functions.
However, When you switch the RDS instance to private, that means it only accepts connections from within the VPC. So you can't make connections directly from your local computer to the database anymore. You have to go through some sort of "bridge" to get your local computer into the AWS VPC network.
In this scenario people either use an EC2 instance as a bastion host, or they create a VPN connection from their local computer into the AWS VPC. AWS Client VPN is a managed service you could used for this.
You'll need to evaluate the Client VPN pricing, but I think you may find that a single t4g.nano
EC2 bastion host is probably cheaper, and you can also stop the instance when you don't need it to really cut down the cost.