In one embodiment, a method is described. The method includes: monitoring workloads of a plurality of application classes, each of the application classes describing services provided by one or more applications in a multi-tiered system and comprising a plurality of instantiated execution resources; estimating, for each of the application classes, a number of execution resources able to handle the monitored workloads, to simultaneously maintain a multi-tiered system response time below a determined value and minimize a cost per execution resource; and dynamically adjusting the plurality of instantiated execution resources for each of the application classes based on the estimated number of execution resources.