FOSS Synapse already is a hybrid of Python and Rust, and has been for years - with Rust used for the hot paths. Synapse Pro is just pushing that a bit further for worker processes, by having the host process itself being Rust-first rather than Python-first. But the majority of the app and architecture is the same; it's just swapping out some of the python-with-rust processes for pure-Rust alternatives. I think of it a bit like using a hardware accelerator (how I envy the fact that nobody complains about the fact that hardware accelerators cost money!)