scalableDimension 
  The scalable dimension. This string consists of the service namespace, resource type, and scaling property.
- ecs:service:DesiredCount- The task count of an ECS service.
- elasticmapreduce:instancegroup:InstanceCount- The instance count of an EMR Instance Group.
- ec2:spot-fleet-request:TargetCapacity- The target capacity of a Spot Fleet.
- appstream:fleet:DesiredCapacity- The capacity of an AppStream 2.0 fleet.
- dynamodb:table:ReadCapacityUnits- The provisioned read capacity for a DynamoDB table.
- dynamodb:table:WriteCapacityUnits- The provisioned write capacity for a DynamoDB table.
- dynamodb:index:ReadCapacityUnits- The provisioned read capacity for a DynamoDB global secondary index.
- dynamodb:index:WriteCapacityUnits- The provisioned write capacity for a DynamoDB global secondary index.
- rds:cluster:ReadReplicaCount- The count of Aurora Replicas in an Aurora DB cluster. Available for Aurora MySQL-compatible edition and Aurora PostgreSQL-compatible edition.
- sagemaker:variant:DesiredInstanceCount- The number of EC2 instances for a SageMaker model endpoint variant.
- custom-resource:ResourceType:Property- The scalable dimension for a custom resource provided by your own application or service.
- comprehend:document-classifier-endpoint:DesiredInferenceUnits- The number of inference units for an Amazon Comprehend document classification endpoint.
- comprehend:entity-recognizer-endpoint:DesiredInferenceUnits- The number of inference units for an Amazon Comprehend entity recognizer endpoint.
- lambda:function:ProvisionedConcurrency- The provisioned concurrency for a Lambda function.
- cassandra:table:ReadCapacityUnits- The provisioned read capacity for an Amazon Keyspaces table.
- cassandra:table:WriteCapacityUnits- The provisioned write capacity for an Amazon Keyspaces table.
- kafka:broker-storage:VolumeSize- The provisioned volume size (in GiB) for brokers in an Amazon MSK cluster.
- elasticache:cache-cluster:Nodes- The number of nodes for an Amazon ElastiCache cache cluster.
- elasticache:replication-group:NodeGroups- The number of node groups for an Amazon ElastiCache replication group.
- elasticache:replication-group:Replicas- The number of replicas per node group for an Amazon ElastiCache replication group.
- neptune:cluster:ReadReplicaCount- The count of read replicas in an Amazon Neptune DB cluster.
- sagemaker:variant:DesiredProvisionedConcurrency- The provisioned concurrency for a SageMaker serverless endpoint.
- sagemaker:inference-component:DesiredCopyCount- The number of copies across an endpoint for a SageMaker inference component.
- workspaces:workspacespool:DesiredUserSessions- The number of user sessions for the WorkSpaces in the pool.