A system and method for determining an optimal cache size of a computing system is provided. In some embodiments, the method comprises selecting a portion of an address space of a memory structure of the computing system. A workload of data transactions is monitored to identify a transaction of the workload directed to the portion of the address space. An effect of the transaction on a cache of the computing system is determined, and, based on the determined effect of the transaction, an optimal cache size satisfying a performance target is determined. In one such embodiment the determining of the effect of the transaction on a cache of the computing system includes determining whether the effect would include a cache hit for a first cache size and determining whether the effect would include a cache hit for a second cache size different from the first cache size.