Event sourcing has a lot of nice properties, so I’m intrigued. But don’t you still need relations? And then how do you implement those?

If the answer is “they’re all implicit in the application layer code” then that’s not really acceptable. I still need some way to query for relations, or keep relation views up to date, or something like that.

I don’t mind if relations are not core to your persistence model, but they have to be implemented _somewhere_ in your data layer, and I’m not seeing any mention of that here.

I have the same issue with Firestore, everyone does relations _somehow_ but it’s all just spaghetti application code which isn’t scalable.