Circuit Breaker
circuit-breaker
System Design
Fault Tolerance, Redundancy & Failover
Fault tolerance is the property that lets a system keep working when components fail - and at any reasonable scale, components are always failing. This lesson covers the building blocks: redundancy (active-active, active-passive), failure detection (health checks, heartbeats), failover (automatic, manual), and the patterns that make systems gracefully degrade instead of catastrophically crash (circuit breakers, retries with backoff, bulkheads, timeouts). We finish with the operational disciplines that turn architecture into reality: chaos engineering, runbooks, blast-radius analysis, and disaster recovery (RTO/RPO). By the end you can design a system that survives the failure modes interviewers love to throw at you.
Service Mesh, Sidecar & Service Discovery
Once you have more than a handful of services, the cross-cutting concerns (mTLS, retries, circuit breaking, load balancing, traffic shifting, observability) start to dominate. Doing them in every service in every language is a maintenance nightmare. The sidecar pattern moves these concerns into a co-located proxy that runs next to your service, and a service mesh is the control plane that programs every sidecar in your fleet from one place. This lesson covers how a mesh actually works (data plane vs control plane, Envoy as the de-facto data plane, Istio and Linkerd as control planes), how service discovery underpins it, and the very real cost (latency tax, complexity, on-call burden) so you know when a mesh helps and when it is over-engineering.
AI Engineering
Design SLOs, rollout, and cost controls
Design reliability controls for a multi-tenant AI assistant: SLOs and error budgets, quota-aware admission, fallback and cost reservations, staged rollout with a canary decision, rollback, and recovery.