For many of us, APIs and their client libraries are the face of our applications to the world. We need to innovate with new features, but breaking changes are toxic to customer trust. In this session you will pick-up concrete design patterns that you can use and anti-patterns that you can recognize so that your service API or library can continue to grow without breaking the world. Using real APIs and open source libraries as a case study, we’ll look at actual examples of specific strategies that you can employ to keep your API backwards compatible without painting yourself into a corner.