Part 2 of “System Design Explained Like a Human.”
This time, we explore how large-scale systems recover when the internet fights back.
💡 1. Fault Tolerance & High Availability
Systems continue running even if parts fail.
Flipkart reroutes traffic to healthy zones within seconds.
Tools: Kubernetes health-checks, AWS ALB, Failover Groups.
🧯 2. Disaster Recovery & Data Replication
Keep live copies in different regions.
Netflix stores in Mumbai + Singapore for failover.
🧩 3. Event-Driven Microservices
Services communicate via events instead of blocking calls.
Example: Swiggy uses Kafka topics between Order, Payment, and Notification services.
⚖️ 4. CAP Trade-offs Revisited
Banking → CP
Social media → AP
Choose what fits your business.
📬 5. Message Queues & Stream Processing
Queues smooth traffic spikes — like taking a token at the bank.
Tools: RabbitMQ, Kafka, Amazon SQS.
🚧 6. Rate Limiting & Circuit Breakers
Protect services from overload and cascading failures.
Libraries: Hystrix, Resilience4J.
🔐 7. Security & API Gateways
Auth every request via JWT / OAuth.
Gateways also log, throttle, and audit traffic.
💸 8. Cost Optimization
Scale up during peak, scale down after.
Use spot instances and reserved capacity.
📈 9. Monitoring & Alerting
Set SLO-based alerts on latency, error rate, and throughput.
Stacks: Datadog, Grafana, Prometheus.
💥 10. Chaos Engineering
Inject controlled failures to test resilience.
Netflix’s Chaos Monkey kills servers randomly.
🧠 11. Data Sharding & Replication Patterns
Shard by user ID / region / hash key to avoid hotspots.
Replicate read-only copies for scale.
🌍 12. Global Systems & Edge Computing
Serve users from the nearest location.
CDNs + edge caching reduce latency.
🩹 13. Auto-Healing Infrastructure
Kubernetes restarts failed pods automatically.
No manual rebooting at 2 AM.
🍔 14. Real-World Case Study — Zomato Order Surge
Health check fails → Pod restarted
LB reroutes traffic
Auto-scaling adds instances
Result: users see a short delay, no downtime.
🏁 Conclusion
From caching and queues to chaos and recovery, this two-part journey showed how modern apps scale and survive.
Great architecture isn’t about preventing failure —
it’s about recovering so fast that no one notices.
If you liked this series, ❤️ it on DEV.to and share with your team.
Let’s keep building systems that don’t just scale — they endure.
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