What do you mean when you say the "story for sharing data between processes isn't really solved"? My understanding of this is mostly academic because I don't personally mix languages all that often, but aren't there many established ways of communication between languages. You have IPC, unix sockets, FFI, protobufs, and other serialising/deserialisation formats. Not to mention the classic (but probably slightly overkill) move of spinning up a local HTTP server and using REST endpoints.