As far as I can tell, Apache Arrow is not very mutable. It basically has to reallocate the universe.
I don't need large data between processes. I need short-lived medium data ... large enough and short-lived enough to make serialization painful but mutable enough to make "stores" kind of annoying.
As far as I understand it, it's more for cross-process in-memory fast access (e.g. numbers crunching), but it's mutable.