Techniques are provided for managing a user space protocol stack are disclosed herein. A nexus in a kernel space can receive a packet from a packet pool, and extract information from the packet to generate a flow key indicating a particular flow for the packet. The nexus can further look up the flow key in a flow table to determine whether there is an existing flow key stored in the flow table matching the flow key of the packet, and store the packet into a batch of packets of the existing flow when the existing flow key matches the flow key of the packet. When a release condition being met, the nexus can release the batch of packets of the existing flow to a user space protocol stack within a user space application through a channel communicatively coupled to the nexus and the user space protocol stack.