##### Question Pick one of your recent projects and walk an interviewer through its architecture end-to-end. Sketch a high-level diagram, then go deep on the design, the trade-offs you made, and how you would evolve it. Be ready for deep-dive follow-ups on any single component. Cover the following: 1. **Diagram & components.** Draw the high-level architecture. Walk through the core components, data stores/data model, external dependencies, and deployment topology (regions, AZs, orchestration). 2. **APIs & data flows.** Describe the key APIs and how data moves through the system: which paths are synchronous vs. asynchronous, and which protocols you used (HTTP/REST, gRPC, message bus). 3. **Design decisions & trade-offs.** Justify your major decisions and the alternatives you rejected. Tie each decision back to constraints such as latency, throughput, and cost. 4. **Scaling & capacity planning.** Explain how the system scales and show how you sized it (QPS, bandwidth, compute). Quantify the key constraints. 5. **Fault tolerance, backpressure, idempotency & retries.** Describe how the system stays up under partial failure — replication, circuit breakers, bounded queues/backpressure, idempotent operations, retry policy, and dead-letter handling. 6. **Observability.** Logging, metrics, and tracing across both synchronous and asynchronous boundaries, and the SLOs/error budgets you tracked. 7. **Security.** AuthN/authZ, secrets management, and PII handling/data protection. 8. **Failure modes you actually hit.** Walk through real incidents: symptom, root cause, how you detected it (alerts/SLIs), how you mitigated it, and the permanent fix — with concrete metrics. 9. **Results & impact.** Share concrete numbers (latency, quality, reliability, cost) that demonstrate the impact of your work. 10. **What you'd redesign.** Given another chance, what would you change, and why?