I recently learned about [SQLite archives](https://www.sqlite.org/sqlar.html) which feel like an interesting option to consider, especially with your comment around sometimes wanting a "binary key-value format" in mind.

Because it's "just sqlite" it's possible to use the archive functionality in archive-like ways, while also using the file as a sqlite db (because that's all it is).

It's not a perfect tool for all scenarios (and I'm thinking it wouldn't be good for backups), but I feel there are definitely some very useful scenarios for it.