1. A system comprising: one or more first computers and one or more storage devices storing instructions that are operable, when executed by the one or more first computers, to cause the one or more first computers to implement a plurality of execution engines, each execution engine being implemented on a particular instance of an underlying computing platform and configured to manage resources in the underlying computing platform according to platform-independent, resource-specific requests received from one or more executors, each request being a request to perform a resource instance-specific operation on the particular instance of the underlying computing platform, and wherein each execution engine is configured to perform operations comprising: performing, for each of the requests, platform-specific, resource instance-specific operations that correspond to the platform-independent, resource-specific request, the platform-specific, resource instance-specific operations being operations specific to the underlying computing platform on which the execution engine is implemented and specific to a particular resource identified by the platform-independent, resource-specific request; and one or more second computers and one or more storage devices storing instructions that are operable, when executed by the one or more second computers, to cause the one or more second computers to implement a plurality of executors, wherein each executor is configured to perform operations comprising: receiving a recipe comprising one or more platform-independent, resource-agnostic commands, each platform-independent, resource-agnostic command a) corresponding to a requested service to be satisfied by providing platform-independent, resource-specific requests to one or more of the plurality of execution engines on an underlying computing platform and b) specifying operations that do not relate to allocating, maintaining, or configuring resources of a particular underlying computing platform, identifying a platform-independent, resource-agnostic Download command in the recipe and in response, generating, using the platform-independent, resource-agnostic Download command, a corresponding first platform-independent, resource-specific request for an execution engine to allocate a first resource on an underlying computing platform, and a corresponding second platform-independent, resource-specific request for the execution engine to copy a target of the Download command into the first resource allocated on the underlying computing platform in response to the first platform-independent, resource-specific request, and identifying a Run command in the recipe and in response, generating, using the platform-independent, resource-agnostic Run command, a corresponding third platform-independent, resource specific request for an execution engine to execute a target of the Run command within the first resource allocated on the underlying computing platform in response to the first platform-independent, resource-specific request, and providing each of the first, second, and third platform-independent, resource-specific requests to a first execution engine of the plurality of execution engines on a first instance of a particular underlying computing platform, wherein the first, second, and third, platform-independent, resource-specific requests cause the first execution engine to perform platform-specific, resource instance-specific operations that allocate the first resource on the first instance of the particular underlying computing platform, copy the target of the Download command into the first resource on the first instance of the particular underlying computing platform, and execute the target of the Run command within the first resource on the first instance of the particular underlying computing platform.