Numba is great for pure functions on primitive types but it breaks down when you need to pass objects around. PyPy is fantastic for single-threaded applications but doesn't play nicely with multiprocessing or distributed computing IME. Numpy helps for stuff you can vectorize, but there's a lot of stuff you can't (or can but shouldn't); it also brings lots of minor inconveniences by virtue of not being a native type - e.g., the code to JSON serialize a `Union[Sequence[float], np.ndarray]` isn't exactly Pythonic.