Inside of Topic is a completely unbounded queue, and that queue can and will fill up if your services start slowing down! Be very, very, very careful of this. There is an open issue to address … but at present it has not been fixed.
You might be wondering how on earth one can then get a computation to run on precisely the pool you want, without having to constantly pass around the explicit reference to the desired pool.
Just imagine if our graphic designer started giving details about the layers they used in Photoshop.