C4 Container Level: System Deployment

Use this skill when

Working on c4 container level: system deployment tasks or workflows
Needing guidance, best practices, or checklists for c4 container level: system deployment

Do not use this skill when

The task is unrelated to c4 container level: system deployment
You need a different domain or tool outside this scope

Instructions

Clarify goals, constraints, and required inputs.
Apply relevant best practices and validate outcomes.
Provide actionable steps and verification.
If detailed examples are required, open resources/implementation-playbook.md.

Containers

[Container Name]

Name: [Container name]
Description: [Short description of container purpose and deployment]
Type: [Web Application, API, Database, Message Queue, etc.]
Technology: [Primary technologies: Node.js, Python, PostgreSQL, Redis, etc.]
Deployment: [Docker, Kubernetes, Cloud Service, etc.]

Purpose

[Detailed description of what this container does and how it's deployed]

Components

This container deploys the following components:

- Documentation: c4-component-name.md

Interfaces

[API/Interface Name]

Protocol: [REST/GraphQL/gRPC/Events/etc.]
Description: [What this interface provides]
Specification: [Link to OpenAPI/Swagger/API Spec file]
Endpoints:
- GET /api/resource - [Description]
- POST /api/resource - [Description]

Dependencies

Containers Used

[Container Name]: [How it's used, communication protocol]

External Systems

[External System]: [How it's used, integration type]

Infrastructure

Deployment Config: [Link to Dockerfile, K8s manifest, etc.]
Scaling: [Horizontal/vertical scaling strategy]
Resources: [CPU, memory, storage requirements]

Container Diagram

Use proper Mermaid C4Container syntax:

C4Container
    title Container Diagram for [System Name]

    Person(user, "User", "Uses the system")
    System_Boundary(system, "System Name") {
        Container(webApp, "Web Application", "Spring Boot, Java", "Provides web interface")
        Container(api, "API Application", "Node.js, Express", "Provides REST API")
        ContainerDb(database, "Database", "PostgreSQL", "Stores data")
        Container_Queue(messageQueue, "Message Queue", "RabbitMQ", "Handles async messaging")
    }
    System_Ext(external, "External System", "Third-party service")

    Rel(user, webApp, "Uses", "HTTPS")
    Rel(webApp, api, "Makes API calls to", "JSON/HTTPS")
    Rel(api, database, "Reads from and writes to", "SQL")
    Rel(api, messageQueue, "Publishes messages to")
    Rel(api, external, "Uses", "API")


**Key Principles** (from [c4model.com](https://c4model.com/diagrams/container)):

- Show **high-level technology choices** (this is where technology details belong)
- Show how **responsibilities are distributed** across containers
- Include **container types**: Applications, Databases, Message Queues, File Systems, etc.
- Show **communication protocols** between containers
- Include **external systems** that containers interact with

API Specification Template

For each container API, create an OpenAPI/Swagger specification:

openapi: 3.1.0
info:
  title: [Container Name] API
  description: [API description]
  version: 1.0.0
servers:
  - url: https://api.example.com
    description: Production server
paths:
  /api/resource:
    get:
      summary: [Operation summary]
      description: [Operation description]
      parameters:
        - name: param1
          in: query
          schema:
            type: string
      responses:
        '200':
          description: [Response description]
          content:
            application/json:
              schema:
                type: object

Example Interactions

"Synthesize all components into containers based on deployment definitions"
"Map the API components to containers and document their APIs as OpenAPI specs"
"Create container-level documentation for the microservices architecture"
"Document container interfaces as Swagger/OpenAPI specifications"
"Analyze Kubernetes manifests and create container documentation"

Key Distinctions

vs C4-Component agent: Maps components to deployment units; Component agent focuses on logical grouping
vs C4-Context agent: Provides container-level detail; Context agent creates high-level system diagrams
vs C4-Code agent: Focuses on deployment architecture; Code agent documents individual code elements

Output Examples

When synthesizing containers, provide:

Clear container boundaries with deployment rationale
Descriptive container names and deployment characteristics
Complete API documentation with OpenAPI/Swagger specifications
Links to all contained components
Mermaid container diagrams showing deployment architecture
Links to deployment configurations (Dockerfiles, K8s manifests, etc.)
Infrastructure requirements and scaling considerations
Consistent documentation format across all containers

c4-container

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