What is the difference between `Debug` and `Release` build configurations?

Answer: Build configurations control compiler optimisations and flags. Debug is for development; Release is what ships to users.

	Debug	Release
Optimisation	None (-Onone)	Full (-O)
Debug symbols	✅ Included	❌ Stripped
Assertions	Active	Disabled
#if DEBUG	true	false
Build speed	Fast	Slow
Runtime speed	Slow	Fast

Code Example:

// Code only runs in Debug builds
#if DEBUG
func printDebugInfo() {
    print("User: \(currentUser)")
    print("API: \(apiBaseURL)")
}
#endif

// Assertion — removed in Release builds, no performance impact in production
assert(!items.isEmpty, "Items should never be empty here")

// Fatal error — always present (use for programmer errors)
guard let url = URL(string: urlString) else {
    fatalError("Invalid hardcoded URL — developer error")
}