An appliance receives packets that are part of a flow pair, each packet sharing an application protocol. The appliance determines an estimated application protocol of the packets without performing deep packet inspection on any packets. The estimated application protocol may be determined by using an application protocol estimation table. The appliance then predicts the inter-packet interval between a packet previously received by the appliance and a next packet not yet received by the appliance. The inter-packet interval may be determined by using an inter-packet interval prediction table. The appliance then preloads packet flow data in a cache before the next packet is predicted to arrive at the appliance. Upon receiving the next packet, the packet flow data is preloaded in the cache. This reduces packet processing time by removing waiting periods previously required to cache packet flow data from an external memory after receiving the next packet.