A system and method is provided for two-tiered load balancing on a hosted voice-over Internet protocol (VoIP) private branch exchange (PBX). The system includes a plurality of client devices, at least one device load balancer, and at least one call load balancer. The device load balancer identifies a device group to which each client device belongs; and a cluster of computing resources for processing calls for the device group. The cluster is assigned to the device group based on prescribed conditions. In response to a communications request, call load balancers in communication with the device load balancers dynamically determine if predefined conditions are currently being met within an identified cluster of computing resources. If the predefined conditions are currently being met, then the communications request for a primary client device associated with the request is established via one of a plurality of server nodes within the cluster of computing resources.