Requires billing alerts to be enabled in your billing preferences & CloudWatchReadOnlyAccess in the role https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/monitor-charges.html

Reference case #5314191201

Updates twice a day

Triggered at the start & end of the working day in Singapore

Deployment notes

Currently the code is defined for my use case and accounts. Notice two accounts are in an organisation and another uses a cross account role to get the metrics.

There are many ways to deploy a serverless function, however I'm using http://apex.run/ in this instance. The project.json looks like:

{
  "name": "estimatedcharges",
  "description": "Post to slack a summary of the estimated charges of the AWS account",
  "profile": "my-profile",
  "memory": 128,
  "timeout": 5,
  "role": "arn:aws:iam::812644853088:role/estimatedcharges_lambda_function",
  "environment": {
	"WEBHOOK": "https://hooks.slack.com/services/XXXXX/YYYYYY/etcetc"
  }
}