We’re working on docs explaining the status of external memory stores, and providing clearer guidance on setting up an external Redis.
A quick summary:
By default, Ray uses its own implementation for an in-memory store (essentially just a hash map).
There is support for an external Redis.
There is no support for other memory stores /yet/, but I believe there is an interface which would allow one to implement such support.
I’m going to shift the label of this question to “Ray Core” so that it gets better attention from the relevant folks.