It is common for cost of a SaaS product to include some dedicated resources, used exclusively by the product, and some shared resources, used by many products. Split Shared Costs Using Telemetry shows how to split the cost of shared resources proportionally among different products. Building on that, we make a new Dimension that combines the shared and dedicated cost.

Split shared cost

This is the CostFormation YAML from the previous telemetry examples. It creates two Dimensions, one to isolate the cost of a Shared Data Lake and a second to split that cost using telemetry into two Elements: Email and Messaging. The element names are specified by the telemetry records not shown here.

Dimensions:
  SharedRDS:
    Name: Shared RDS
    DefaultValue: Not Shared
    Rules:
      - Type: Group
        Name: Shared Data Lake
        Conditions:
          - Source: Service
            Equals: AmazonRDS
  SplitDataLake:
    Type: Allocation
    Name: Split Data Lake
    AllocateByStreams:
      Streams:
        - rds-writes-by-product

Create a Product Dimension

The following is the YAML to create a Product Dimension.

...
  Product:
    Name: Product
    DefaultValue: Other
    Rules:
      - Type: Group
        Name: Email
        Conditions:
          - Source: Tag:Product
            Equals: email
      - Type: Group
        Name: Messaging
        Conditions:
          - Source: Tag:Product
            Equals: messaging
      - Type: GroupBy
        Source: User:Defined:SplitDataLake

Group Rules

First, we create a Group rule for each product type. In this example we only have two: Email and Messaging. Each rule uses Conditions to specify the resources used exclusively by that product. In this simple case these resources are identified simply by an AWS tag. In a real world case this would most likely be more complex.

GroupBy Rule

The final rule is a GroupBy used to add in the shared cost from the SplitDataLake Dimension created earlier. Since that Dimension uses the same element names, Email and Messaging, the result combines the shared and dedicated cost. This is shown in the preceding YAML for creating a Product Dimension:

      - Type: GroupBy
        Source: User:Defined:SplitDataLake

ℹ️

The approach is the same for creating a Product Dimension where the split is done with a Proportional Allocation Dimension. The main difference is that the Source of the GroupBy rule would be adjusted to reference the Proportional Allocation Dimension.