I need to load stuff from a database into my ecs structure at some point... How would you do that normally ? My current idea is the following... Start of frame -> Create X archetypes ( entities ) -> Let multiple specialized database systems load their stuff into the created entities -> Process main frame logic... i bet this is better than doing the database loading stuff somewhere in the middle of the frame right ?

If you have a method that works for you, use it.

If the method does not work for you, ask here about how to solve the specific problem it's giving you.