title: Tracking changes in data with Firebase
body: <p>I'm really interested in the synchronized database paradigm championed by Firebase and others (Couchbase Sync Gateway for example). It really does a great job in replacing 80% of what an API does, which is storing and retrieving data. But usually, that's not all an API does. While we are storing and retrieving data, we are also doing non-data related stuff like sending emails or push notifications. To do those things, I should be able to intercept data changes and do something when a new record is created, when an existing record is changed in a certain way, or when a record is deleted. Parse has a great mechanism for that in its Cloud Code (<a href="https://parse.com/docs/cloud_code_guide#functions-aftersave" rel="nofollow">https://parse.com/docs/cloud_code_guide#functions-aftersave</a>) but I couldn't find something similar in Firebase. Did I miss something or am I thinking of it the wrong way?</p>