> And we decided that each system processes relevant entity data by iterating through entities first. Now we have another problem - growing the number of entities slows down every system, even the ones that are not related...

Call me out if I'm wrong, but I don't know of any high-performance ECS framework that actually does this. Most frameworks maintain sorted collections of components with no gaps. For instance, if I want all entries with X,Y,Z, then I iterate those three arrays starting at their X,Y, Z section, and the order of components in that section of the arrays matches exactly (meaning we can just iterate through them all).

This library seems like a really neat concept, but I think the ECS concepts that it's critiquing aren't actually used in many production-quality frameworks. Call me out if I'm just missing context here.

Also, I'd love more details on how CGS is able to always iterate on flat vectors with no gaps. The only way I've seen to accomplish this is to do a decent amount of work curating components into multiple orderings, so if CGS is avoiding that, I am equal parts skeptical and very very excited (since that would be super useful!)