> I'll there fore be running Python alongside the Clojure/JVM stack.

Yikes, really? That sounds even worse than a clean break. You don't shed your perceived problems with Python and instead get to manage two codebases and stacks. Your operations team will absolutely love you in the future.

Based upon a casual read of what your service does, I'm really stressing to think of a CPU-bound situation that can't be pooled into a multiprocessing pool. All of the heavy work I can think of your service doing -- particularly crawling -- is going to end up network or I/O-bound, isn't it? I'm coming up empty and working with a theory. Perhaps you can share what your CPU-bound process is?