This is the answer - http://mirror.tallysolutions.com/Downloads/TallyTips/GettingStartedwithDataSynchronisation.pdf
Thanks to @MitaleeRao...
Edit placed here for brevity:
These are 2 points I've noted regarding the Tally architecture:
- The database is a flat file in a tree structure, and there are numerous checkpoints at each level for maintaining this inheritance (for e.g., a voucher has inventory entries that have stock items, which have units, etc.).
- The SOAP XML protocol that Tally uses does not have multi-threading capabilities - i.e., the Tally server will only accept one request and give a response at a time.
The Data syncronisation that Tally has introduced is probably the automating of exporting the XML of all masters/vouchers and importing them onto the central Database (whether on the Tally.NET server or on a local computer with a static IP). Not sure how the Google Drive client works, but I'm assuming it is a variation of the same (i.e., XML based data export and then import onto a main computer).