Circuit breaker with Resilience4j in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary purpose of a circuit breaker in microservices?

Select the main reason why a circuit breaker pattern is used in microservices architecture.

A To cache responses from a service to improve performance

B To encrypt communication between microservices for security

C To balance load evenly across multiple instances of a service

D To prevent a service from repeatedly calling a failing downstream service and allow it to recover

💡 Hint

Think about how to avoid cascading failures when a service is down.

The circuit breaker stops calls to a failing service temporarily, allowing it to recover and preventing cascading failures.

❓ Architecture

intermediate

Which component in Resilience4j handles the state transitions of a circuit breaker?

Identify the Resilience4j component responsible for managing the states (closed, open, half-open) of a circuit breaker.

A CircuitBreaker

B Bulkhead

C CircuitBreakerRegistry

D Retry

💡 Hint

This component directly wraps the protected function and tracks failures.

The CircuitBreaker interface manages the state transitions and decides whether to allow calls or not.

❓ scaling

advanced

How does Resilience4j's circuit breaker behave under high concurrent load when many calls fail?

Consider a scenario where many concurrent requests to a downstream service fail. What will the circuit breaker do to handle this load?

A It scales the number of circuit breakers dynamically based on load

B It immediately opens the circuit after the failure threshold is reached, blocking further calls until reset

C It ignores failures under high load to maintain throughput

D It queues all requests and retries them sequentially to avoid overload

💡 Hint

Think about how the circuit breaker protects the system from overload.

When failure rate exceeds the threshold, the circuit breaker opens to block calls, preventing overload and allowing recovery.

❓ tradeoff

advanced

What is a tradeoff when setting a very low failure rate threshold in Resilience4j circuit breaker?

If you configure the circuit breaker with a very low failure rate threshold (e.g., 1%), what is a likely tradeoff?

A The circuit breaker may open too frequently, causing unnecessary blocking of calls

B The circuit breaker will never open, ignoring real failures

C The circuit breaker will consume excessive memory resources

D The circuit breaker will cause increased network latency

💡 Hint

Think about sensitivity to failures and how it affects call blocking.

A very low failure threshold causes the circuit breaker to open often, even for minor or transient failures, which can reduce availability.

❓ component

expert

In a Spring Boot application using Resilience4j, which annotation enables declarative circuit breaker support?

Choose the correct annotation to apply on a method to enable circuit breaker functionality with Resilience4j in Spring Boot.

A @EnableCircuitBreaker

B @Resilience4jCircuitBreaker

C @CircuitBreaker(name = "backendService")

D @CircuitBreakerEnabled

💡 Hint

Look for the annotation that specifies the circuit breaker name directly on the method.

The @CircuitBreaker annotation from Resilience4j is used on methods to enable circuit breaker behavior declaratively.