Connected Cloud API provides a near-time mechanism for data exchange based on the availability of the target Connected Cloud application. So, with this in mind, you maybe wonder how could you know when the data requested is available for being downloaded and processed, or if maybe a polling policy should be implemented in order to keep track of each data refresh.
The answer is no, you don't need to perform any extra implementation to really know when fresh data has been uploaded by the Connected Cloud application.
During the on-boarding process, where you registered the application being developed, you had to provide a notification URL. As you maybe noticed at this point, this callback address has been used to provide your application with the API key required each time a passcode that you have generated is granted by any user at the Connected Cloud application side. But this is not the unique goal of it.
Apart from the initial usage to provide you with the API keys, this notification URL will be used by the Connected Cloud API any time it needs to inform you that there is new data available and also to provide feedback about the ingestion process of the data provide by your application to be processed and ingested by the Connected Cloud application. All details about every notification provided using this URL could be found here.
With this approach, you don't have to worry about when new data has been delivered but neither dealing with extra implementation or weird processes to guess it.
Just be aware on your own application development and rely on the Connected Cloud service to keep you up to date.