A policy associated with a notification received by one or more computer systems is obtained. A first request is submitted, to a service, for a first current capacity of a resource. An amount by which to adjust a capacity of the resource is calculated, based at least in part on the policy and the first current capacity. A second request is submitted, to the service, to adjust the capacity of the resource by the amount. A third request is submitted, to the service, for a second current capacity of the resource, and whether the second request has been fulfilled is determined based at least in part on a comparison between the second current capacity and the response to the third request.