Agile Architecture - Changing Application Servers

Some projects are simply too big to finish on the release schedule that you want to maintain. Rally\´s agile engineering team delivered a very disruptive architectural change lasting nine months in parallel with three releases. This paper will show how this was done without prolonging the usual release cycles and without technically crippling our product or doing a lot of throwaway work. The main elements of our approach were: the "sacrifice one" pattern, incremental delivery of the architectural change when possible, technical infrastructure modifications to support incremental changes to the architecture, and addressing the biggest risk first. When we were close to finished, we added the whole team for the final push to release with the new architecture. The end result was three successful releases of the existing system prior to the final release rolling out the new architecture.