We present a performance analysis technique for dis- tributed real-time systems in a setting where certain com- ponents are modeled in a purely functional manner, while the remaining components require additional modeling of state information. The functional models can be efficiently analyzed but have restricted expressiveness. On the other hand, state-based models are more expressive and offer a richer set of analyzable properties but are computation- ally more expensive to analyze. We show that by appro- priately composing these two classes of models it is pos- sible to leverage on their respective advantages. To this end, we propose an interface between components that are modeled using Real-Time Calculus [Chakraborty, K?unzli and Thiele, DATE 2003] and those that are modeled us- ing Event Count Automata [Chakraborty, Phan and Thia- garajan, RTSS 2005]. The resulting modeling technique is as expressive as Event Count Automata, but is amenable to more efficient analysis. We illustrate these advantages using a number of examples and a detailed case study.