prd-v06-architecture-design_skill

Overview

This skill defines how system components connect during PRD v0.6 Architecture, turning stack selections, risks, and feature needs into concrete architecture decisions. It produces ARC- entries that record choices, rationale, alternatives, and consequences. The outputs feed the v0.6 Technical Specification and drive downstream implementation, security, and operations work.

How this skill works

The skill pulls TECH- (technology choices), RISK- (constraints and threats), and FEA- (feature requirements) to shape boundaries, component placement, and integration patterns. It maps component relationships, picks patterns for build vs buy items, and writes ARC- decision records with context and rationale. Diagrams, trust boundaries, and quality gates are created to ensure each major decision has an associated ARC- entry.

When to use it

• When asked to design architecture, system design, or component connectivity
• After TECH- stack selection and before drafting the technical specification
• When high-priority RISK- entries need architectural mitigations
• When deciding how Buy/Integrate services will connect or be abstracted
• When you need documented decisions for downstream teams (security, infra, dev)

Best practices

• Start with a modular monolith for MVP; extract services only with evidence
• Map each high-priority RISK- to at least one ARC- mitigation decision
• Abstract critical vendors behind adapter layers if switching is plausible
• Define clear trust boundaries and data flow before detailing components
• Record every major decision as an ARC- entry with alternatives and consequences

Example use cases

• Choose between monolith, modular monolith, or microservices based on TECH- and RISK- inputs
• Define an adapter layer for authentication provider to avoid vendor lock-in
• Design webhook handling: verify signature, idempotency, enqueue events, then process
• Document caching and read-replica strategy to address scaling RISK-007
• Produce ARC- entries for security (JWT strategy), performance (CDN/caching), and devops (CI/CD)