IPC methods were actually used when constructing the foreign API prototype, since if you do not use JPype, the JVM must be launched in its own process. The IPC methods were used on the API level, with the JVM starting its own CPython interpreter, with CPython and Java using `cloudpickle` to send each other functions/objects.

Using IPC for all internal calls would probably take significant overhead; the user functions are typically small (think `lambda shift: shift.date in employee.unavailable_dates` or `lambda lesson: lesson.teacher`). Depending on how many constraints you have and how complicated your domain model is, there could be potentially hundreds of context switches for a single score calculation. It might be worth prototyping though.