If a user-facing API relies on a backend service that often fails, what design pattern can prevent the user-facing API from repeatedly trying to call the failing service and instead give an immediate error or fallback?

The design pattern that prevents a user-facing API from repeatedly trying to call a frequently failing backend service and instead provides an immediate error or fallback is the Circuit Breaker pattern. This pattern operates like an electrical circuit breaker, which trips and opens a circuit when it detects a fault, preventing damage and allowing time for recovery. Its primary purpose is to stop the calling service from wasting resources on a failing dependency, prevent cascading failures, and improve the user experience by providing faster feedback.