In reply to Thierry Muller.

@Thierry Muller When unsure about technical details about performance and caching, what about looking at real world solutions in other plugins like yoast or similar which have millions of active installs and seem to work fine.

And trying to providing new core features ready for sites with "X million posts" seems to be a nice thing, but the rest of core, especially Gutenberg, won't be able to handle this anyway, just try Gutenberg with a few hundred categories or tags which a X million posts site probably will have...