"Application file format" is the thing which intrigues me. I think people don't think about it as an option enough, it should be used more frequently. File form

"Application file format" is the thing which intrigues me. I think people don't think about it as an option enough, it should be used more frequently. File format versions backed by migrations, trivial inspection of data, transactional for free, you can keep recent history of changes, hierarchy etc. It's pretty good.