When do you consider implementing a circuit breaker pattern

hey everyone, ive been thinkin a lot about distributed systems lately and how fragile they can be. weve all seen those cascading failures where one service goin down takes out half the system. im curious when you all start thinkin about intro-ing the circuit breaker pattern to mitigate these issues. is it when you hit a certain number of external dependencies, a specific error rate threshold, or is it more of a gut feelin based on the criticality of the services involved? whats your go-to strategy for decidin if and when to implement this