In cache enabled networks, either memory or backhaul is used to deliver files from a core network to a transmitter. To support a high level of wireless quality of service (QoS), network resources including small base stations, memory, and backhaul are required. In this letter, while satisfying a wireless QoS constraint, memory, and backhaul for the whole network are minimized. For a given density of small base stations, optimal memory size is found in closed-form. Also, the optimal density of SBSs is numerically obtained to minimize the total memory and backhual required to satisfy the QoS.