1. A method comprising: maintaining, by a processor, a record of computing resources in both (i) a cloud computing environment and (ii) an additional cloud computing environment external to the cloud computing environment, wherein available computing resources in the cloud computing environment and the additional cloud computing environment are determinable from the record of computing resources; receiving, by the processor, a request to instantiate a virtual machine in the cloud computing environment; determining, by the processor, in response to the request to instantiate the virtual machine, that the cloud computing environment lacks the available computing resources to support the virtual machine in view of the record of computing resources; in response to the determining that the cloud computing environment lacks the available computing resources to support the virtual machine: determining, by the processor, that a set of inactive reserve resources in the cloud computing environment cannot support the virtual machine; in response to the determining that the inactive reserve resources of the cloud computing environment cannot support the virtual machine: determining, by the processor, that computing resources in the additional cloud computing environment are sufficient to support the virtual machine in view of the record of computing resources; and in response to the determining that computing resources in the additional cloud computing environment are sufficient to support the virtual machine: instantiating, by the processor, the virtual machine using computing resources provided by the additional cloud computing environment.