What Is the Circuit Breaker Pattern—and Why Is
It Critical for Modern Microservices?
In today’s world of distributed systems, microservices constantly
communicate with each other. This approach gives us flexibility and
scalability, but it also introduces a common problem: when one service
starts to fail, those failures can easily spread and impact the entire
system.
The Circuit Breaker is designed to stop this chain reaction. Instead of
repeatedly calling a service that’s already having trouble, it temporarily
stops incoming requests and gives the system a chance to recover. Think
of it as a simple safety net that helps your application stay responsive
even when things go wrong.
In this article, we’ll walk through the Circuit Breaker Pattern from a
developer’s point of view—how it works, why it’s useful, and when you
should consider using it in your microservice-based applications.
What Is the Circuit Breaker Pattern?
The Circuit Breaker, as the name suggests, is a resilience pattern that
helps manage service-to-service calls in a safe and controlled way. Its
main goal is to prevent failures in one service from negatively affecting
others.
Let’s explain this with a real-life example from an e-commerce
payment system. In modern software architectures, services are highly
interconnected—payment services, product inventory services, shipping
services, bank APIs, and more. Each of these services depends on others
to function properly, which makes failure handling a critical concern.
If one of these services goes down, its impact can grow like a line of
dominoes and eventually paralyze the entire system. This is exactly
where the Circuit Breaker Pattern steps in.
Just like an electrical fuse in real life, a circuit breaker in software does
the same thing: it cuts off the problem before it grows bigger.
Why Do We Need a Circuit Breaker?
Think about this scenario:
You’re on an e-commerce website trying to complete a payment. The
payment is processed through a bank’s API. During a campaign period,
the bank API becomes overloaded—it sometimes takes 20–30 seconds
to respond, sometimes doesn’t respond at all, and sometimes completely
goes down.
If a single payment request takes 25 seconds, that’s a disaster for a
large e-commerce platform handling thousands of payments per second.
The payment can’t be completed → the user abandons the order →
revenue is lost.
But it gets worse.
The payment service keeps sending requests to the bank API, slowly
exhausting its thread pool. Eventually, the entire e-commerce system
becomes unresponsive. This is where the Circuit Breaker truly
becomes a lifesaver.
How Does the Circuit Breaker Work?
A Circuit Breaker has three main states:
The system is operating normally. All requests are sent to the bank API.
Errors and timeouts are continuously monitored.
For example, if 10 out of the last 20 requests fail, the failure rate
reaches 50%, and the circuit transitions to the Open state.
In this state, no requests are sent to the bank at all.
The reasons are simple:
In an e-commerce scenario, the best possible action at this point is:
✔ Fallback logic is triggered
The user receives a message like:
“Your bank is currently not responding. Your payment could not be
completed, but your order has been placed in Pending status. We will
retry the payment shortly.”
Thanks to this approach:
The system only stops communicating with the bank—everything else
continues to work.
After a predefined wait time (for example, 10 seconds), the Circuit
Breaker performs a check:
“Is the bank API healthy again?”
It sends 1–2 test requests:
This allows the system to recover automatically without manual
intervention.Circuit Breaker in an E-Commerce Payment Flow –
Summary
In a real-world e-commerce environment, the payment flow looks like
this:
payment”
Conclusion
The Circuit Breaker Pattern is one of the most critical safety
mechanisms in modern microservice architectures.
It is especially vital for systems such as:
As seen in the real-world e-commerce example above:
Circuit Breaker = better user experience + protected revenue
+ a resilient systemReferences
https://martinfowler.com/bliki/CircuitBreaker.html?source=
post_page-----909126bd00b9---------------------------------------
https://gokhana.medium.com/circuit-breaker-pattern-nedir-
6d36f2fc35d0
https://gurcanozdecan.medium.com/circuit-breaker-pattern-
nedir-8e441c99b405
By Halime Öztürk