My google app engine app sometimes throws deadline exceeded errors when processing a form submit due to an extremely chatty back and forth with a filemaker database backend which winds up taking longer than the 1 minute maximum.

I figure I could improve this by using an appengine task to process the data POSTed from the form, and instead immediately render a response page such as "Your order is being processed, please wait."

Is there a way to determine when the app engine task has completed on the browser/client side so I can render a "Success" page when the order completes? What would be the best way to do this?