Data traffic of different customers or tenants can be efficiently handled at a shared node while still being isolated from each other. An application instance can create multiple network stack that are isolated from each other and intelligently manage threads across the isolated network stack instances. To intelligently manage the threads across the network stack instances, each thread maintains data that identifies the network stack to which the thread is assigned. With this information, the application can intelligently use a thread already assigned to a network stack that will process the data traffic and avoid the performance impact of a system call to assign the thread to the network stack.