Since your system is backed by Oracle, the question is whether Ash still brings enough to justify adoption. I think it does. The auth system, validation, the action pipeline, and the structure Ash brings to your domain more than pay for themselves. It is also low risk to try. Pick one slice of your domain and wire it up to your existing API. If it does not feel worth it, you can step back out easily.

If someone is starting a new Elixir project and considering Oracle for persistence, I would be cautious. You can build an Ash extension, but you will own all the quirks that come with Oracle’s closed system, including its types, pagination rules, DDL quirks, and JSON behavior. You will get no support from Oracle, and because most Elixir developers work with open-source projects, you are likely to find less community help.