This video was one of the sessions during our Event-Driven Microservices Conference 2020. If you had a 50-year-old legacy system based on mainframe technology, how would you go about modernizing it? Recently we had an opportunity to participate in such a project. Modernization of a system this large and complex can only be done in phases, using the Strangler pattern and implementing new ways of interacting with the end users. For providing brand new user experience, we have built a set of user-facing applications that are independent but still communicate and exchange data and events. And this is where Axon Framework really shined. During the project, we have faced some challenges but looking in hindsight we have also found an acceptable solution for each one of them. And now we're turning lessons learned from using Axon Framework in a complex legacy environment to an open-source Project Klokwrk, hoping others will benefit from our experiences.