Beginner LevelSystem Design & Architecture
What is the Circuit Breaker Pattern and how does it prevent cascading system failures?
❓ Interview Prompt: Explain Circuit Breakers, Closed, Open, and Half-Open states, failure thresholds, and preventing cascading failures across microservices.
The Circuit Breaker Pattern wraps remote network calls to prevent a failing downstream service from causing cascading failure across an entire system:
3 States:
1
🟢 Closed (Normal): Requests pass through to the downstream service.
2
🔴 Open (Failing): Downstream error threshold exceeded. Circuit trips open immediately; all subsequent calls fail fast or execute fallbacks without calling the failing service!
3
🟡 Half-Open (Testing): After a cooldown timer, limited trial requests test if the downstream service has recovered.
Code Implementation Example
markdown
Circuit Breaker State Machine:
┌──────────┐ (Failures > Threshold) ┌──────────┐
│ Closed │ ───────────────────────> │ Open │
└──────────┘ └──────────┘
▲ │ (Cooldown Timer)
│ (Trial Success) ┌──────────┐ │
└──────────────────────── │Half-Open │ <┘
└──────────┘💡Circuit Breaker state transition machine.
🎯 Interview Key Takeaway
Wrap downstream network calls with Circuit Breakers to fail fast and prevent cascading microservice outages.
#System Design#Circuit Breaker#Resilience#Fault Tolerance#Beginner
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