1. A method, comprising: generating, in a data interface of a distributed computing system, a first pool health index value for a first pool of servers based on a comparison of forecast demand data that estimates a number of virtual machine instances needed at a future time in the first pool of servers configured to host virtual machine instances with forecast capacity data that includes an indication of a number of slots estimated to be available to run virtual machine instances in the first pool of servers at the future time; determining, in a control interface of the distributed computing system, a plurality of increased capacity configuration options for the first pool of servers; generating an overall system health assessment value for each of the plurality of increased capacity configuration options; comparing each of the assessment values to determine a configuration option of the plurality of increased capacity configuration options having a greatest health increase assessment value; and in response to the first pool health index value being less than a threshold value implementing the determined configuration option, wherein implementing the determined configuration option comprises: reconfiguring a server that is configured to host a first virtual machine instance type in a second pool of servers to host a second virtual machine instance type in the first pool of servers; launching available hardware to host a virtual machine instance of the second virtual machine instance type in the first pool of servers; or evicting a virtual machine instance running on a server in the first pool of servers.