1. A computer implemented method of optimizing systems usage, the computer implemented method comprising: a processor receiving a work request; the processor decomposing the work request into units of work; the processor retrieving a first unit of work from the units of work; and the processor selectively sending the first unit of work to a first system or a second system for execution based on a first work constraint on the first unit of work, wherein the first work constraint limits execution of the first unit of work to a system that is compliant with an execution environment rule for the first unit of work.