HEIC Images
Use HEIC instead of jpeg (~50% the size, similar quality).
It also let:
to Store auxiliary images (depth, disparity, and so on)
Supports alpha
Lossless compression
Multiple images in a single container
Available from iOS 11.
Assets Catalog
Use AssetsCatalog for free optimizations like app slicing and more.
Drive Usage
Try to minimize read/write of files in disk, even on small files (<4KB).
Don’t use info.plist and JSON files as databases, use core data instead.
CoreData has CloudKit integration with iOS 13.
Lots of tips on SQLite performance.
File Activity Instrument
Use the File Activity Instrument to see how your app behaves file-wise.
The session ends with a 10 minutes overview on the file activity instrument, where the guy explains how to use the system cache as much as possible.
