1. A non-transitory computer-readable storage medium having computer-executable instructions stored thereon which, when executed by a computer, cause the computer to: scale, according to a first set of rules, virtual machine instances associated with a customer of a computing platform that comprises a plurality of availability zones for providing the virtual machine instances, wherein the first set of rules are defined by the customer and comprise rules for a particular action to be taken when one or more conditions occur and wherein the particular action comprises instantiating new virtual machine instances or terminating existing virtual machine instances; compute a probability that a capacity of the plurality of the availability zones for providing virtual machine instances will be available during a capacity event, the capacity event reducing the capacity of the availability zones by causing one or more of the virtual machine instances associated with the customer to become unavailable; modify the first set of rules based upon the computed probability to generate one or more modified rules; cause the virtual machine instances to be scaled utilizing the modified rules in the absence of the capacity event; receive a notification that the capacity event has occurred in the computing platform; in response to receiving the notification, scale the virtual machine instances associated with the customer during the capacity event according to a second set of rules defined by the customer; determine that the capacity of the plurality of availability zones has been restored following the capacity event; and in response to determining that the capacity of the plurality of availability zones has been restored, scale the virtual machine instances associated with the customer according to the first set of rules.