How to efficiently use asyncio when calling a method on a BaseProxy?

Unfortunately, the multiprocessing library is not suited to conversion to asyncio, what you have is the best you can do if you must use BaseProxy to handle your IPC (Inter-Process communication).

While it is true that the library uses blocking I/O here you can't easily reach in and re-work the blocking parts to use non-blocking primitives instead. If you were to insist on going this route you'd have to patch or rewrite the internal implementation details of that library, but being internal implementation details these can differ from Python point release to point release making any patching fragile and prone to break with minor Python upgrades. The _callmethod method is part of a deep hierarchy of abstractions involving threads, socket or pipe connections, and serializers. See multiprocessing/connection.py and multiprocessing/managers.py.

So your options here are to stick with your current approach (using a threadpool executor to shove BaseProxy._callmethod() to another thread) or to implement your own IPC solution using asyncio primitives. Your central database-access process would act as a server for your other processes to connect to as a client, either using sockets or named pipes, using an agreed-upon serialisation scheme for client requests and server responses. This is what multiprocessing implements for you, but you'd implement your own (simpler) version, using asyncio streams and whatever serialisation scheme best suits your application patterns (e.g. pickle, JSON, protobuffers, or something else entirely).

A thread pool is what you want. aioprocessing provides some async functionality of multiprocessing, but it does it using threads as you have proposed. I suggest making an issue against python if there isn't one for exposing true async multiprocessing.

https://github.com/dano/aioprocessing

In most cases, this library makes blocking calls to multiprocessing methods asynchronous by executing the call in a ThreadPoolExecutor