A Circuit Breaker is a pattern used to make microservices resilient and self-healing by protecting the system as a whole from problems in its component services, allowing for independent status and reducing the impact of transient failures and bugs. In contrast to traditional monolithic applications, each service in a microservice architecture can have multiple instances running, making it easier to add redundancy and improve resilience. Circuit Breakers can be integrated with RPC to handle interoperability bugs and provide a safety net against delayed errors. The use of circuit breakers is not limited to individual services but can also be applied to the routing layer between services, providing vital information about the health of the microservices ecosystem.