Alright so the caveat of going with a json based database model and keeping it all in memory is that there's a recommended maximum of memory you can keep at a time, or you risk your app crashing.
However, according to this: https://stackoverflow.com/a/29094983
For newer iPhones that's somewhere between 1GB and 2GB, which is a massive amount of data for a json database, something stupid like like ~7.5m to ~15m records. So for _most_ applications, if you also do some purging of ancient records, you'd be fine
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