---

name: architecture-patterns description: Provides guidance on software architecture patterns and design decisions. Use when designing systems, choosing patterns, structuring projects, or when asked about architectural approaches.

Architecture Patterns Skill

Pattern Selection Guide

By Project Size

By Team Size

Common Patterns

1. Layered Architecture

Copy┌─────────────────────────────┐
│       Presentation          │  ← UI, API Controllers
├─────────────────────────────┤
│       Application           │  ← Use Cases, Services
├─────────────────────────────┤
│         Domain              │  ← Business Logic, Entities
├─────────────────────────────┤
│      Infrastructure         │  ← Database, External APIs
└─────────────────────────────┘

Use when: Simple CRUD apps, small teams, quick prototypes

2. Clean Architecture

Copy┌─────────────────────────────────────┐
│            Frameworks & Drivers      │
│  ┌─────────────────────────────┐    │
│  │     Interface Adapters       │    │
│  │  ┌─────────────────────┐    │    │
│  │  │   Application       │    │    │
│  │  │  ┌─────────────┐    │    │    │
│  │  │  │   Domain    │    │    │    │
│  │  │  └─────────────┘    │    │    │
│  │  └─────────────────────┘    │    │
│  └─────────────────────────────┘    │
└─────────────────────────────────────┘

Use when: Complex business logic, long-lived projects, testability is key

3. Hexagonal (Ports & Adapters)

Copy        ┌──────────┐
        │ HTTP API │
        └────┬─────┘
             │ Port
    ┌────────▼────────┐
    │                 │
    │   Application   │
    │     Core        │
    │                 │
    └────────┬────────┘
             │ Port
        ┌────▼─────┐
        │ Database │
        └──────────┘

Use when: Need to swap external dependencies, multiple entry points

4. Event-Driven Architecture

CopyProducer → Event Bus → Consumer
              │
              ├─→ Consumer
              │
              └─→ Consumer

Use when: Loose coupling needed, async processing, scalability

5. CQRS (Command Query Responsibility Segregation)

Copy┌─────────────┐      ┌─────────────┐
│  Commands   │      │   Queries   │
│  (Write)    │      │   (Read)    │
└──────┬──────┘      └──────┬──────┘
       │                    │
       ▼                    ▼
  Write Model          Read Model
       │                    │
       └────────┬───────────┘
                ▼
           Event Store

Use when: Different read/write scaling, complex domains, event sourcing

Directory Structure Patterns

Feature-Based (Recommended for medium+)

Copysrc/
├── features/
│   ├── users/
│   │   ├── api/
│   │   ├── components/
│   │   ├── hooks/
│   │   ├── services/
│   │   └── types/
│   └── orders/
│       ├── api/
│       ├── components/
│       └── ...
├── shared/
│   ├── components/
│   ├── hooks/
│   └── utils/
└── app/
    └── ...

Layer-Based (Simple apps)

Copysrc/
├── controllers/
├── services/
├── models/
├── repositories/
└── utils/

Decision Framework

When making architectural decisions, consider:

1. Simplicity - Start simple, evolve when needed
2. Team Skills - Match architecture to team capabilities
3. Requirements - Let business needs drive decisions
4. Scalability - Consider growth trajectory
5. Maintainability - Optimize for change

Trade-off Analysis Template

Copy## Decision: [What we're deciding]

### Options Considered
1. Option A: [Description]
2. Option B: [Description]

### Trade-offs
| Criteria | Option A | Option B |
|----------|----------|----------|
| Complexity | Low | High |
| Scalability | Medium | High |
| Team familiarity | High | Low |

### Decision
We chose [Option] because [reasoning].

### Consequences
- [What this enables]
- [What this constrains]