Logging is important, I think anyone that has wrote software knows that. But this is your PSA to do better.

There are too many messaging services in AWS. SNS, SQS, and EventBridge are the usual suspects, so we'll go over what each is good at and when to use them.

Using multiple regions in the same system can be troublesome when using IaC. This is one area where Terraform shines compared to CloudFormation.

How many Security Groups does your application need? There's no right answer, sorry for the rhetorical question.