How do you evolve a framework over nearly two decades without losing the trust of millions of developers? In this talk, I will reflect on 19 years of working on Spring, the Java application framework—from the early days of XML configuration, through the rise of annotations, to the advent of functional programming.

I will share the lessons that come not just from designing APIs and writing code, but from practicing open source stewardship over time. That includes how to innovate under constraints, how to evolve APIs responsibly, how to serve a growing community, and why empathy and restraint are essentials skills when it comes to maintaining open source.

This talk is for anyone willing to learn from my past mistakes, so they can make entirely new ones.