RESTful APIs have become standard in our industry. A good REST API provides a simple, lightweight means of building customizations and integrations. However, many of the quick, high value integrations we’d like to build require knowing when something happened. Consider building an event API, which, when used in conjunction with a REST API, facilitates simple workflow, notification, and synchronization integrations. These integrations often require no more than 20 or 30 lines of code. Often event APIs take the form of a “web hook” or callback mechanism, but don’t be afraid of using a poll-based Atom style either. An Atom event API scales cheaply and gives the client the power to guarantee delivery.