What problem does it solve? Writing system design documentation often produces vague diagrams and hand-wavy claims like "high traffic" instead of concrete numbers, making it hard for engineers and stakeholders to evaluate or implement an architecture. This Skill enforces a rigorous structure with quantified requirements, capacity estimation, and documented trade-offs. ## Core Features & Use Cases - Structured Design Process: Walks through requirements definition, scale estimation, high-level design, component detailing, scaling plans, failure analysis, and decision documentation. - Concrete Output Template: Produces documents with ASCII architecture diagrams, API contracts with real request/response JSON, database schemas, cache strategies, and cost estimates. - Complete Worked Example: Includes a full URL shortener design covering PostgreSQL schema, Redis caching, base62 ID generation, failure scenarios, monitoring alerts, and AWS cost breakdown. - Use Case: When planning a new service handling 1B requests per month, use this Skill to produce a design doc with capacity math, component specs, failover plans, and a deployment timeline that your team can review and execute against. ## Quick Start Use the system-design-doc skill to create a design document for a notification service handling 10 million users with p99 latency under 200ms.
