Tips for concurrent access to get_prices

I would like to know the best method to execute concurrently a lot of calls to the 'get_prices' function to process data from the usstock minute database.

Currently, I'm using the Pool object from the Multiprocessing module but it seems that at most only four calls are executed to get_prices concurrently.

Can get_prices be called safely by several processes concurrently?

Is there any limit?

This is covered in the docs: Usage Guide