My Keycloak journey started more than eleven years ago. Just one year later, after my first integrations and contributions, I wrote my first SPI implementation: a UserStorageProvider. To this day, it's the extension I've built more often than any other, followed by Authenticators, Required Actions, Realm Resources, credential handling, custom SPIs, and many more. I do this not just for a living. But for the love of living.

In this talk, I'll share what I've learned along the way: which strategies worked (and still do), which ones didn't, and why. I'll also cover my best practices for dependencies, version upgrades and migrations, for testing extensions properly, and, increasingly relevant, for building extensions with the help of AI agents.

You’ll leave with concrete patterns you can apply to your own extensions right away, and hopefully skip a few of the mistakes I’ve already made for you.