Fixflo provides support for webhooks, also known as callbacks or service hooks.

A webhook enables third-party applications to be notified if a particular event happens in Fixflo. These are messages sent by Fixflo to configured third parties about changes made to Fixflo entities and are sent when those changes happen. This enables a third party to know about changes sooner without needing to poll Fixflo’s api.

Technical information can be found here