> * They need to use lightweight object for buffer.  At least,
> memoryview object is large (192byte
>  on Python 3.7.3 amd64).

Actually it is larger, because you should add the size of internal objects. In 3.8:

>>> sys.getsizeof(memoryview(b''))
184
>>> sys.getsizeof(gc.get_referents(memoryview(b''))[0])
128

312 bytes total, not counting padding. The average size of co_code in Lib/*.py is 85 bytes. Unless Instagram uses gigantic functions and methods (and no comprehensions or lambdas), the net benefit will be negative.