1. A system to deliver an application, hosted by a private application provider, over a network to a user device comprising: an application delivery system that includes at least one CPU and at least one non-transitory storage device configured to provide, a first network interface that includes a plurality of first network interface instances that includes multiple second connection endpoints; a network security interface that includes a plurality of security interface instances that each includes multiple second connection endpoints and multiple fourth connection endpoints; a second network interface that includes a plurality of second network interface instances that each includes multiple third connection endpoints; and multiple application agents, disposed within one or more private application provider systems; a first information structure in the at least one non-transitory storage device that associates first network interface instances with one or more security interface instances; a second information structure in the at least one non-transitory storage device that associates second network interface instances with one or more security interface instances; wherein respective first network interface instances are configured to receive one or more user or device requests for access to a hosted application and in response to each received user or device request, to create a respective second network connection with an associated security interface instance, wherein each respective second connection includes one endpoint within a respective first network interface instance and includes one endpoint within an associated security interface instance, and to send the received user or device request to the associated security interface instance over the respective second network connection; wherein respective second network interface instances are configured to have respective pools of respective third network connections with one or more agents and to have corresponding respective fourth connections with one or more associated security interface instances, wherein each respective fourth connection includes one endpoint within a respective second network interface instance and includes one endpoint within an associated security interface instance; and wherein respective security interface instances are configured to receive one or more user or device requests from respective first interface instances and in response to each received user or device request, to determine whether the received user or device request is valid, and in response to determining that the received user or device request is valid, to couple a respective second network connection endpoint to a respective fourth network connection endpoint, and to send the received user or device request over the a respective coupled fourth network connection for delivery to a respective agent over an associated third network connection.