I understand the API will change, but will the JSON representation in such a way that it's not safe to use currently? I don't mind a bug here and there, but it would be quite serious not to be able to use old content with a new version of the editor.
This seems dodgy. Is planetscale behind Vitess? If you press the "Learn more about Vitess" button you get to a page that gives you the impression that it is the homepage of Vitess (and that it is their product). But the actual website of vitess (https://vitess.io) mentions nothing of planetscale and the people behind it. Additionally, planetscale are displaying users of Vitess which makes it look like they are also users of planetscale.