Circuit breaker pattern in Microservices - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the Circuit Breaker pattern in microservices?

It is a design pattern that stops calls to a failing service to prevent system overload and allows recovery by retrying after some time.

beginner

Name the three main states of a Circuit Breaker.

Closed (normal operation), Open (calls blocked), Half-Open (test if service recovered).

intermediate

Why is the Half-Open state important in the Circuit Breaker pattern?

It allows the system to test if the failing service has recovered by allowing limited calls before fully closing the breaker.

beginner

What happens when the Circuit Breaker is in the Open state?

All calls to the failing service are blocked immediately to prevent further failures and resource waste.

intermediate

How does the Circuit Breaker pattern improve system resilience?

By preventing cascading failures, reducing load on failing services, and allowing graceful recovery.

Which state of the Circuit Breaker allows limited calls to test service recovery?

A Closed

B Half-Open

C Open

D Disabled

The Half-Open state allows some calls to check if the service is healthy again.

What does the Circuit Breaker do when it detects repeated failures?

A Ignores failures

B Closes to allow all calls

C Restarts the service

D Opens to block calls

It opens to stop calls and prevent further failures.

Why is it important to block calls to a failing service?

A To reduce load and avoid cascading failures

B To increase traffic

C To log errors only

D To restart the client

Blocking calls reduces load and prevents failures from spreading.

In which state does the Circuit Breaker allow all calls to pass through?

A Closed

B Open

C Half-Open

D Disabled

Closed state means normal operation with all calls allowed.

What triggers the Circuit Breaker to move from Open to Half-Open?

A Manual reset

B Service restart

C Timeout expires

D Error count increases

After a timeout, the breaker tries limited calls in Half-Open state.

Explain the Circuit Breaker pattern and its states in simple terms.

Think of a real circuit breaker in your home that stops electricity when overloaded.

Describe how the Circuit Breaker pattern helps improve reliability in microservices.

Imagine stopping calls to a broken phone line to avoid wasting time and resources.