Designing architectures for interactive systems is difficult: Many system failures are due to the inability to handle social and technical changes that occur during development. We present two architectural patterns for interactive systems. We applied these to a short-term and a long-term development project. In the WebbviceLT Project, the conceptual model was modified to handle various extensions and to meet an emerging standard. In the Dragon Project, the user interface evolved significantly over a period of almost two years. The application of these two architectural patterns demonstrates how focusing on change, or more specifically on architectural uncertainty, can be crucial to the success of a project.