What number of stack technologies can be used in one application?

Any number of stack technologies can be used in an application, depending on the architecture and requirements of the project. For example, in an iOS application, the following are typically used:

• Programming language (Swift, Objective-C)
• UI frameworks (UIKit, SwiftUI)
• Networking libraries (Alamofire, URLSession)
• Databases (Core Data, Realm)
• Testing tools (XCTest)

Additionally, the application may interact with a server-side component, use third-party SDKs, analytics services, etc. Thus, the number of technologies in the stack can range from a few to dozens, with the main goal being that they integrate well and support the application's objectives.