Abstract: A resource management system of a computing resource service provider supports the provisioning of multiple identical or substantially similar virtual computing resource instances using a single resource definition by creating a resource set entity to which the provisioned instances belong. The resource management system controls the provisioning based on a template containing the resource definition and designed to service a situation where the intent is to create a group of similar or closely-related resources. The group of instances (i.e., items in the resource set) can be dimensioned by specifying the size of the set, or by mapping the set to another set of keys associated with a different context. A resource set definition in the template can include a program expression that the system evaluates to produce a list of the keys, and the instances may be created based on the number of keys and their associated values.