Circuit Breaker with Resilience4j

Stops calling a failing downstream service temporarily, so one slow/broken dependency can't cascade into a full outage.

@CircuitBreaker(name = "paymentService", fallbackMethod = "fallback")
public String callPaymentService() {
    return restTemplate.getForObject("http://payment-service/pay", String.class);
}

public String fallback(Exception ex) {
    return "Payment service unavailable, try again later.";
}

CLOSED — calls pass through normally
OPEN — calls fail immediately without hitting the downstream service
HALF_OPEN — a few test calls are allowed through to check if the service recovered