And I understand that a significant proportion of Azure is running VMs with headless copies of Word hooked up to Office 365 so that those same old documents can

And I understand that a significant proportion of Azure is running VMs with headless copies of Word hooked up to Office 365 so that those same old documents can straightforwardly be opened online, too. Apologies I can't find the reference (of course I read this on here). I'm very curious if a) the VM stays open the whole time, b) your document gets exported to some kind of perfect serialization format that can then be re-saved when you're done, c) if Word is using something like operational transformations to store keystrokes and edits and then ticker-taping that into a save routine, or d) something else.