Amazon S3 datastore

[Nitiks25]

Hello, 

To use a datastore for persisting DAM files, as per documentaiton we have to use appropriate config files.
Depending on that, either FileStore or S3DataStore will be used.
I'm trying to understand, which class or set of classes decides which store to use (File / S3), depending on the configuration used?
In other words, which would be the calling class using the datastore?
Just trying to understand the datastore flow.
Thanks!

[smacdonald2008]

This doc is the closest information set applicable to this question: https://docs.adobe.com/docs/en/aem/6-2/deploy/platform/data-store-config.html.