@carlw @mikehearn Thanks for your recommendations!
@amanda.hinchman-dominguez Actually I already began implementing a "backend" using TornadoFX JSON capabilities. My approach was quite simple: 1 JSON file per collection of items. But I'm not sure this will scale well when loading larger collections.
I'm working on a budgeting software for personal use - so I need to read and store files like for example a word processor does. But I'm struggling with the format. I really would like some sort of basic SQL (nothing super fancy, only things like querying all transactions with a given account or map&fold a collection of transaction to a final balance). However I don't think a H2/HSQLDB + Hibernate setup is really the thing I want. Some middle ground would be nice. Not worrying about how/when the data is actually stored on disk and having a simple querying interface.