AWS Custom Config Rules --- The Configuration_Item
The Configuration_Item is the document that holds information about resources. This way you can build evaluations from the Configuration_Item.
In this instance, our evaluation scope is AWS::EC2::Instances and so each EC2 instance make up a configuration_item which then is subject to an evaluation (either "Compliant" or 'Non_Compliant' based on what is being specified).
In this video we're working with instance-id's and usernames in tags, in terms of how we're evaluating compliance of the ec2's, though there are so many different custom rules you can build with resources in the configuration_item: https://markcodebucket.s3-us-west-1.a...
Here is a demo custom_config lamda that relies on you specifying the usernames that are acceptable to have as the Name tag. If the EC2 isn't properly tagged according to Name: username[i], then it's considered "NON_COMPLIANT"
https://markcodebucket.s3-us-west-1.a...
Please reference this excellent official repo with a good set of boiler plate functions that handle the refresh functions, error handling, of sdk interacting with the config system as well as typical scenarios with configuration items...
https://github.com/awslabs/aws-config...