I read some of the discussions on the topics on the internet inspired by your question, and I think that it is (somewhat) of a shared interpretations that ECS can be thought as an in-memory relational database. Though, in respect to other kinds of in-memory databases it is mostly optimized for raw speed and flexibility in operations related to simulations/games. In the end, queries in Ark just iterates over homogeneous arrays so the speed is sort of as good as it can get on these operations.
I find a bit hard to understand what ACSets does since the algebraic viewpoint is a bit unfamiliar to me and at the same time the documentations is very brief. What I can see is that the performance can’t most probably match the one in Ark since its API is not enough “type-based” so it is probably type unstable in some places, but I have to say I don’t really understand how to write an equivalent Ark program with ACSets.