system-design-basics

# System Design Basics Skill

> **Purpose**: Atomic skill for system design fundamentals with validated parameters and production-ready patterns.

## Skill Identity

| Attribute | Value |
|-----------|-------|
| **Scope** | Scalability, Reliability, Availability |
| **Responsibility** | Single: Foundational design patterns |
| **Invocation** | `Skill("system-design-basics")` |

## Parameter Schema

### Input Validation
```yaml
parameters:
  design_context:
    type: object
    required: true
    properties:
      problem:
        type: string
        minLength: 10
        maxLength: 500
        description: "Clear problem statement"
      scale:
        type: object
        properties:
          users: { type: integer, minimum: 0 }
          qps: { type: integer, minimum: 0 }
          data_size: { type: string, pattern: "^\\d+[KMGTP]B$" }
        required: [users]
      constraints:
        type: array
        items: { type: string }
        maxItems: 10

validation_rules:
  - name: "scale_consistency"
    rule: "qps <= users * 100"
    error: "QPS seems unreasonably high for user count"
  - name: "required_context"
    rule: "problem.length >= 10"
    error: "Problem statement too vague"
```

### Output Schema
```yaml
output:
  type: object
  properties:
    architecture:
      type: object
      properties:
        components: { type: array }
        data_flow: { type: string }
        trade_offs: { type: array }
    capacity:
      type: object
      properties:
        storage: { type: string }
        bandwidth: { type: string }
        compute: { type: string }
    recommendations:
      type: array
      items:
        type: object
        properties:
          area: { type: string }
          suggestion: { type: string }
          priority: { type: string, enum: [high, medium, low] }
```

## Core Patterns

### Scalability Patterns
```
Horizontal Scaling:
├── Stateless Services
│   ├── No session affinity
│   ├── Externalize state (Redis, DB)
│   └── Contain