Kotlin‑SDK for managing game achievements

Imagine you are interviewing at a company that develops mobile games. The company has concluded that implementing an achievement system increases player retention and engagement. You are required to create an SDK that allows tracking, modifying, and requesting player achievements within the game. The games are built on different engines (e.g., Unity), but may call Kotlin classes. You need to design an architecture that will keep track of user achievements and update them in real-time.