Microservices Resilience: Scenario-Based Questions

In distributed systems, failures are inevitable. Circuit breakers act as safety valves to prevent one failed service from dragging down the entire system — especially under load.

💡 What Is a Circuit Breaker?

• Monitors request failures and opens the circuit after threshold breaches.
• Stops sending requests to downstream until a cooldown or manual reset.
• Protects from retry storms and overloads during outages.

⚙️ Circuit Breaker States

• Closed: Normal operation; all calls go through.
• Open: Calls are blocked or fast-failed.
• Half-Open: Allow limited probes to check recovery.

🛠️ Libraries and Tools

• Java: Resilience4j, Hystrix (legacy)
• Go: gobreaker, resilience-go
• Node.js: opossum
• Istio/Envoy: Circuit-breaking at the service mesh layer

🔧 Key Parameters

• Failure threshold: e.g., 50% errors in last 10 requests
• Timeout duration for open state
• Backoff strategy for retries

✅ Best Practices

• Log circuit transitions (open, close, half-open) for observability.
• Combine with bulkheads and retries for full resilience.
• Integrate with alerts when circuits stay open too long.

🚫 Common Pitfalls

• No fallback logic when the circuit opens.
• Improper thresholds — causing too many false positives.
• Silent circuit breakers — failing without visibility.

📌 Final Insight

Circuit breakers are your first line of defense in microservices failure isolation. When designed with telemetry, fallback, and tuning, they keep your system stable under chaos.