Is circuit breaker pattern applicable for asynchronous requests also?

I am new to microservice architecture. I found lots of examples to implement circuit breakers in synchronous requests.

But do we need circuit breakers in asynchronous request flows also?

The Circuit Breaker Pattern is mostly applicable for synchronous service communication. It is meant to avoid that a service is becoming overwhelmed with requests, and that the clients start to retry the requests so that the situation gets even worse.

In an asynchronous, event-driven architecture, services put events on a broker, and consumers reads events in its own pace - so the producer and the consumer is decoupled so it does not have the same problem as with synchronous communication between services.