What constitutes a new application version? This question is not easy to answer from a technical point of view. Modern distributed application architectures make it harder, since they require versioning at multiple points. In this presentation, Oliver outlines many of the common difficulties you will encounter in an event-sourced application system. What to do when event structures change? Can read models be migrated? How do I test the new version before publication? What about running versions side-by-side? Oliver will address these questions and many more, and useful hints for your first event-sourced application, the version update to v1.0, round off the presentation.