krishujeniya/aegis/architecture-c4-model

C4 Architecture Documentation

Use this skill to design or document the architecture of a software system following the C4 Model.

Overview

The C4 model consists of 4 levels of diagrams:

1. Context Level: High-level system context with personas and user journeys (focuses on people and external software systems, not technologies).
2. Container Level: Maps applications and data stores. Shows high-level technology choices, deployment containers with API documentation.
3. Component Level: Defines the components within a container.
4. Code (Optional): Deep code-level implementation details.

How to Apply During Project Planning

When asked to design the system architecture, always walk through the levels:

1. Context Diagram & Documentation

• Define the user personas (Who is using this system?)
• Define external systems (What APIs or platforms does it interact with?)
• Create a C4Context Mermaid diagram showing the system in the center.

2. Container Diagram & Documentation

• Break the system down into Deployable Units (e.g., PostgreSQL Database, Next.js Frontend, Python FastAPI Backend).
• Define the exact technologies chosen for each container.
• Create a C4Container Mermaid diagram detailing how these containers interact.

3. Component Definition

• Inside the backend, what are the core modules? (e.g., Auth Module, Billing Module, Search Service).
• Detail boundaries, API contracts, and bounded contexts (DDD).

Deliverables to Generate

When using this skill to plan architecture, output:

1. System Context Overview (c4-context.md)
2. Container Deployments (c4-container.md or a detailed README section)
3. Mermaid Architecture Flow using C4Context or C4Container notation.