Successful smart services require seamless integration into existing corporate systems and an interdisciplinary approach that aligns the development of both business models and technical architectures. Multidisciplinarity and co-creating with customers add a layer of complexity but are essential collaboration schemes for validating the value proposition of smart services and building long-term customer loyalty. This paper explores these challenges and distills the design principles for the architectures of technical smart service systems, based on empirical data from architecture projects in two manufacturing companies. These principles contribute to the sparse academic literature on this topic and help practitioners navigate several design trade-offs commonly arising in smart service projects.