It looks like the Metricbeat AWS Billing module takes in an arbitrary number of Cost Explorer Group by Dimensions, and then iterates over them individually to generate documents.
Ideally it should allow you to pair up dimension keys, as you can send 2 at a time to the API. The best example of this, is if you're using a consolidated billing account.
In the current config, you can pull the "SERVICE" and "LINKED_ACCOUNT" Dimensions. Which gives you two groups of documents.
- How much you spent per service across all accounts.
- The total cost of each account.
This means it's impossible to drill down and see a breakdown of what happened in each account.
The AWS API does allow two dimensions in one request. In which case metricbeat would receive every unique pair of Account and Service type. Which would be a much more usefull data set.