Tomorrow's immersive applications will leverage Mixed Reality interfaces accessing a multitude of services from distributed clouds. They will face extreme latency constraints, massive datasets, spontaneous collaboration, and constant service churn. This paper outlines our experience evolving an application designed to support collaborative work in Urban Design (UD) practices. The application, UD Co-Spaces, recently weathered significant churn as a core service was discontinued and replaced by a service with a subtly different API. A “dumb pipes” approach, where services communicate through a simple message queue, facilitated this evolution with relatively little disruption to the rest of the system. We show how this strategy can be used to reintroduce new features to the system, and is sustainable as the system's interfaces evolve to use Virtual, Augmented and Mixed Reality environments.