Yeah... that's the approach to take: a backend like this is gonna be a docker compose kinda thing, with orchestrated pieces, anyway... regardless of language.
Python's a great language for prototyping, so with the SDK idea in mind... anything written in prototype Python that is not public in the SDK could be rewritten later in another (faster) language -- either piecemeal with C modules or in entirety.
I'm just spitballing, here, but I'm really warming to this idea.