You might be interested in some of the presentations at KeyConf[0]. You can also get some real world stories from the Reddit[1].

I was at KubeCon EU this year (representing my employer, FusionAuth) and there were lots of folks who were running Keycloak who came and chatted with us.

It's a different set of tradeoffs than Auth0 or other SaaS services. More control, but more responsibility too.

0: https://events.linuxfoundation.org/kubecon-cloudnativecon-eu...

1: https://www.reddit.com/r/KeyCloak/

I've seen it used in production by larger orgs. The scale where you plan for around 6 months of migration, customization and integration of your legacy zoo with 7 different user account DBs. On one hand, all of these projects were successful and now run it in production. On the other, they all really needed the 6 months to whip it into shape.

Edit: Meaning I would use it if you need to get up and running quickly, but it's a solid foundation to build on long-term.

For what it's worth Authentik has been listing Cloudflare as a customer for a while. Worth a look. There might be something in their blog.

Yes! I used keycloak for multitenant auth and it worked fine - a little dated but functional. Nowadays I'd probably stick to something like Clerk/BetterAuth/Supertokens.