---
title: "What is Circuit breakers?"  
description: "What is Circuit breakers?"  
author: "Anubhav Sharma"  
published: 2026-02-05  
updated: 2026-02-09  
canonical: https://www.mindstick.com/forum/162028/what-is-circuit-breakers  
category: "website & mobile applications"  
tags: ["cloud computing", "api(s)", "cloud"]  
reading_time: 3 minutes  

---

# What is Circuit breakers?

What is [Circuit](https://answers.mindstick.com/qa/44582/the-union-government-has-sanctioned-rs-98-35-cr-for-the-development-of-a-heritage-circuit-in-which-indian-state) breakers, [Explain](https://www.mindstick.com/forum/157854/what-is-system-debugging-explain-some-system-debugging-tools-used-in-modern-computer-systems) with example?

## Replies

### Reply by ICSM Computer

Circuit breakers are a **resilience pattern** used in software systems to **prevent repeated failures from cascading and taking down your whole app**.

Think of it like the electrical circuit breaker in your house.

## The simple idea

If a remote service (API, database, SMTP server, payment gateway, etc.) keeps failing:

- Don’t keep hammering it
- Don’t block threads waiting forever
- Don’t spread the failure to other parts of your system

Instead:

- **Trip the circuit**
- **Fail fast**
- **Recover gracefully**

That’s a circuit breaker.

## Why circuit breakers exist

Without a circuit breaker:

- Your app calls a failing service
- Requests time out
- Threads pile up
- CPU/memory spike
- Your entire system slows down or crashes

With a circuit breaker:

- Detect repeated failures
- Stop calling the broken service temporarily
- Return a fallback response immediately
- Periodically test if the service is healthy again

## Circuit breaker states

A circuit breaker has **three states**:

### Closed (normal state)

- Requests flow normally
- Failures are counted
- If failures cross a threshold → **Open**

### Open (tripped)

- Calls are **blocked**
- Requests fail immediately
- No waiting, no retries
- After a cooldown period → **Half-Open**

### Half-Open (testing mode)

- Allows a few trial requests
- If they succeed → **Closed**
- If they fail → **Open again**

## Real-world example

Imagine your **Newsletter Worker Service** sending emails:

- SMTP server goes down
- Every retry takes 30 seconds
- 1000 queued emails = disaster

With a circuit breaker:

- After, say, 5 failures → circuit opens
- Emails fail fast
- Worker stays healthy
- After 1 minute → test SMTP again

## Circuit breaker vs Retry

These two work **together**, not against each other:

| Pattern | Purpose |
| --- | --- |
| Retry | Handle **temporary** glitches |
| Circuit Breaker | Handle **persistent** failures |

Best practice:

- Retry **inside**
- Circuit breaker **outside**

## Circuit breakers in .NET (Polly)

In .NET, circuit breakers are usually implemented using **Polly**.

Conceptually:

```cs
Policy
    .Handle<Exception>()
    .CircuitBreaker(
        exceptionsAllowedBeforeBreaking: 5,
        durationOfBreak: TimeSpan.FromSeconds(60)
    );
```

This means:

- 5 failures → circuit opens
- Stays open for 60 seconds
- Then tries again

## When should you use circuit breakers?

Use them when calling:

- External APIs
- Email/SMS gateways
- Payment services
- Databases over the network
- Microservice-to-microservice calls

Avoid them for:

- In-memory operations
- Pure CPU logic
- Deterministic code

## Key takeaway

> A circuit breaker **protects your system from repeatedly calling something that is already broken**, allowing it to recover instead of collapse.


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Original Source: https://www.mindstick.com/forum/162028/what-is-circuit-breakers

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