Disadvantage: Core Data is slow and hard to speed up so that it isnt a problem.

I am now working on iOS for 14 years — and at the beginning I believed in the same benefits as you.

But midway through my career I noticed, that all of this becomes trivial, if you just dont give the control out of your hand.

You want speedy search: maintain an index of words.

The converting isnt needed, if you implement "Codable" — and only mirrors the serialisation to SQLite in CD.

Updating the set does not necessarily require you to change all content — no-one says that you have to keep it in one file.

of course you also just can encrypt the data as needed.

Every developer should be able to create this in a few days — and adapt it from there for different apps and uses cases.