How scalable is Ash?

Are there currently limitations that developers should be aware of? Does it play nice with, for example? Does it take up a lot of resources?

No issues that I’m aware of. I’ve deployed plenty of Ash apps to fly. I don’t have any numbers off the top of my head, but I haven’t seen anything that differs from running something like vanilla phoenix/ecto code, aside from that calling an Ash action may be a few ms slower than calling an ecto query directly (in the same way that calling a context function would be slower than a query directly, its doing more things).