What is GoogleDocs worth?

Question

Google

Guys, it's very interesting to know how GoogleDocs is designed on the server side. Interested in a way to store data:
- What type of database is used (how is data of this type generally stored)?
- How is the document revision mechanism implemented?
- How is the undo/redo mechanism implemented?
Maybe the guys from Google themselves talked about this, or do you have any information on this? If anyone knows, then share, very interesting.

Answer 1

They keep the Docs architecture a big secret (there are no competitors).
Most likely spanner + GAE (internal).

Answer 2

That's what I thought, but what if we store the document as RTF or ODF? Surely there are some implementations for implementation in the web. For example, there is a webodf library that displays ODF documents.
How do you think this approach works?