You might be thinking having started to read this blog that the primary use case of Data Replication API’s is to provide replication, well yes and no! No in a sense it won’t replicate your data for you, it actually won’t even return your data. What it will do is tell you what record Id’s have been updated or deleted within a certain time frame. What happens next is up to you, you don’t even have to do any replication if you don’t want to!
As someone who loves to keep things as native as possible, when answering this StackExchange post, i found it quite cool to find that this API is actually available to Apex developers! The API consist of two Database class methods getUpdated and getDeleted. The former returns new and updated records, its up to you to decide if its a new record or existing depending on if you’ve seen the record Id before or not.
Note: The process around these API’s is explained in more detail in the SOAP Developers Guide, so its worth reading this along with the Apex Developers Guide references. The general polling process is described here and limits and considerations here.
The API’s could not be easier to use, the following shows how to pull a list of record Id’s for updates made to records for a given object in the last hour.
Database.GetUpdatedResult r = Database.getUpdated( 'MyObject__c', Datetime.now().addHours(-1), Datetime.now());

Salesforce documentation relating to the latestDateCovered field
Neither methods appear to consume any query or DML governor limits, though as noted above have some limits of their own. The GetUpdatedResult (described in more detail in the SOAP API documentation) contains a latestDateCovered field. This value should be retained and used in subsequent getUpdated calls.
Its unclear what Salesforce means by safety in the documentation, though the note relating to long running batch processes does make sense. This aspect highlights a key difference between attempting to query whats changed yourself based on the audit fields. The getDeleted method also works in the same way.
Its worth considering these API’s as a possible and lighter alternative to using Apex Triggers or UI’s to invoke custom behaviour when records are manipulated. Unlike Triggers you don’t know the specific changes, though Field Audit information could be queried if needed.
So be it a replication to another cloud via an Apex HTTP Callout or simply monitoring record activity into some org wide stats. Having Apex support allows you to keep things native via an Apex Schedule job to poll this API as often as you wish. With the advent of External Objects aka Lightning Connect other native possibilities start to present themselves…
