On what principles is it recommended to implement caching to optimize system performance?

Caching implementation for system performance optimization in iOS (and in general) is based on several principles:

• Data locality: cache should store data that is frequently used or accessed.
• Size limitation: cache should not occupy too much memory, so it is important to set limits and a cleanup policy.
• Replacement policy: determine which data to remove from cache when it is full (e.g., LRU — Least Recently Used).
• Data consistency: cache should be updated or invalidated when the source data changes to avoid stale information.
• Asynchrony: loading and updating cache is better done asynchronously to avoid blocking the main thread.

In iOS, NSCache is often used — a class that implements cache with automatic memory management and object removal policies when resources are low.

Example of using NSCache:

let imageCache = NSCache<NSString, UIImage>()

func cacheImage(_ image: UIImage, forKey key: String) {
    imageCache.setObject(image, forKey: key as NSString)
}

func getCachedImage(forKey key: String) -> UIImage? {
    return imageCache.object(forKey: key as NSString)
}