Unrelated to the post – but if you're trying to build smt that "magically syncs" across devices, you'd like to use CouchDB (and it's front end companion, PouchDB). They solve this problem for you, and it's solved in a very, very reliable way for years!
FWIW, search [and research] about offline-first apps. Lots of gems in this niche!
FWIW, search [and research] about offline-first apps. Lots of gems in this niche!