notice scalability issues in gitlab

howto/gitlab.md

@@ -1002,6 +1002,13 @@ A few ideas on tools:
  * [Mediawiki spam control tricks](https://m.mediawiki.org/wiki/Manual:Combating_spam)
  * [Friendly CAPTCHA](https://friendlycaptcha.com/), [considered for inclusion in GitLab](https://gitlab.com/gitlab-org/gitlab/-/issues/273480)
 
+### Scalability
+
+We have not looked a lot into GitLab scalability. Upstream has
+[reference architectures](https://docs.gitlab.com/ee/administration/reference_architectures/) which explain how to scale for various
+user sizes. We have not yet looked into this, and so far have just
+thrown hardware at GitLab when performance issues come up.
+
 ## Issues
 
 [File][] or [search][] for issues in the [gitlab project][search].