Section 6: Five Boxes, Fully Defended - High-Level Architecture & Component Design

Executive Summary: This section assembles the complete architecture — static frontend on a CDN, managed API gateway, one stateless serverless function, one managed key-value table, and observability threaded through everything. We conduct the compute deliberation (serverless versus always-on container versus VM fleet) with a full verdict table, trace both request journeys end to end with their failure behavior named at every hop, and then perform the review that distinguishes Staff candidates: defending the components that are deliberately absent. The architecture that emerges is one an engineer can hold entirely in their head — which is precisely the point.

The whiteboard moment arrives. The interviewer hands you the marker: "Draw it." And here the gravitational pull of every architecture you've ever admired begins to work against you — the service mesh, the cache tier, the event backbone, the twelve microservices arranged like a citadel. Resist. Section 3's arithmetic measured this system at 120 requests per second and 60 megabytes; the architecture must obey that measurement. The candidates who fail this moment fail it by drawing the citadel. The candidates who pass draw five boxes — and can defend, with numbers, why every missing box is missing.

The Whole System on One Whiteboard

Name a concrete incarnation — it signals you've shipped, not just sketched: on AWS, CloudFront + API Gateway + Lambda + DynamoDB; on Azure, Static Web Apps + Functions + Cosmos DB; on GCP, Cloud CDN + Cloud Run + Firestore. Same shape, different logos, one day of work.