1. A learning-based computer network security system, comprising: one or more hardware processors; a network security service delivery controller executing on one or more of the hardware processors, the network security service delivery controller operable to receive network flow attributes associated with a network flow, the network flow to be sent to one or more destination machines via a communication network, the network security service delivery controller further operable to group the network flow into a similarity group at least based on the network flow attributes, wherein the network security service delivery controller groups a plurality of network flows into a plurality of similarity groups, the network security service delivery controller further operable to designate a network security appliance instance from a plurality of network security appliance instances for a particular similarity group, wherein the network security service delivery controller designates each of the plurality of similarity groups respectively to a network security appliance instance in the plurality of network security appliance instances, the network security service delivery controller further operable to direct transmission of the network flow to the network security appliance designated for the similarity group associated with the network flow.