"Both cloudformation stacks were identical (instance names, etc)."

This is why it's a good practice to include the environment name in the resource names when it makes sense. Even better, don't append the env name, but use it as a prefix, like ProdCustomerDb instead of CustomerDbProd. I also like to change the theme to dark mode in the production environments as most management UIs support this. One other neat trick is to color code PS1 in your Linux instances, like red for prod, green for dev.