Embodiments of the present invention provide an application execution controller, configured to instruct an execution of an application in a computing environment having a plurality of different amounts and/or types of a plurality of categories of computing resource to allocate to executing applications; the controller comprising: an information collecting unit, configured to collect: available resource information detailing a plurality of configurations of computing resources available to execute the application, wherein the configurations each include an indication of an amount and/or type of computing resource available in each of the plurality of categories of computing resource; application execution scalability information including, for computing resources in at least one of the plurality of categories, an indication of how different amounts and/or types of computing resource in that category correlate with execution rate of all or a portion of the application; and performance target information including an indication of one or more performance targets for the execution of the application. The application execution controller further comprises: a configuration selection unit configured to perform a selection of a configuration from among the plurality of configurations detailed in the available resource information which, based on the application execution scalability information, will meet, or will come closest out of said plurality of configurations to meeting, the one or more performance targets; and an instructing unit configured to instruct the computing environment to execute the application using the selected configuration.