(my response to https://twitter.com/apotonick/status/717105889845624832)
I haven't yet came across readily available resources for large-scale application architecture for Elixir apps. I found Programming Phoenix to be a good start for that though. And there's ~30 years of knowledge in the Erlang land :)
For web apps, I found the abstractions that Elixir/Phoenix provides to be really helpful. Indeed, the list below is somewhat ORM focused.
In the small, Ecto.Schema, Ecto.Query, Ecto.Changeset, and Phoenix.View allow me to build highly composable and side-effect free modules. I can have many schemas, changesets and queries all interacting with the same underlying DB table(s) if I want to. Most of the side-effects (through Ecto.Repo for DBs) are usually in the Phoenix.Controller (or other Plugs).