BG event updating on rails

Hello, i have an e commerce application that gets the product prices
from an
external service, the service sometimes takes a few seconds to respond,
there will be many user accessing the site. There are custom products so
cant just pull all the prices, i have to request it for each cart and re
evaluate every time the cart is updated.

I have a solution that i would like to hear second opinions on. I think
could use beanstalk and faye to update the clients cart. Moving the
resquest to a beanstalk daemon and updating my app via faye. I am just
use the negative implication and if there is a better way to update the
after that has been a background process.

Suggestions will be very appreciated

I am just not sure of the negative implication