domains / software-engineering / backend-architecture-design / architecture-patterns

architecture-patterns

Skill card

combined

The copies split into two distinct procedural styles. The Vibe-Skills and openclaw-master-skills copies are identical, detailed reference documents that embed the core concepts (Clean, Hexagonal, DDD) and a full Python implementation example directly in the skill. The antigravity-skills and agentic-awesome-skills copies are shorter, procedural wrappers that define a 4-step workflow (clarify, select, define, migrate) and defer the details to an external resource file. The agentic-awesome-skills copy adds a specific constraint regarding durable execution (DBOS) for failure-prone workflows. Because one set contains the actual implementation patterns while the other contains the workflow steps and a specific infrastructure constraint, crowning one would hide the other's material content.

Repositories

Other copies

Combined skill

---
name: architecture-patterns
description: Implement proven backend architecture patterns including Clean Architecture, Hexagonal Architecture, and Domain-Driven Design. Use when architecting complex backend systems or refactoring existing applications for better maintainability.
---

# Architecture Patterns

Master proven backend architecture patterns including Clean Architecture, Hexagonal Architecture, and Domain-Driven Design to build maintainable, testable, and scalable systems.

## When to Use This Skill

- Designing new backend systems from scratch
- Refactoring monolithic applications for better maintainability
- Establishing architecture standards for your team
- Migrating from tightly coupled to loosely coupled architectures
- Implementing domain-driven design principles
- Creating testable and mockable codebases
- Planning microservices decomposition

## Do Not Use This Skill When

- You only need small, localized refactors
- The system is primarily frontend with no backend architecture changes
- You need implementation details without architectural design

## Instructions

1. Clarify domain boundaries, constraints, and scalability targets.
2. Select an architecture pattern that fits the domain complexity.
3. Define module boundaries, interfaces, and dependency rules.
4. Provide migration steps and validation checks.
5. For workflows that must survive failures (payments, order fulfillment, multi-step processes), use durable execution at the infrastructure layer — frameworks like DBOS persist workflow state, providing crash recovery without adding architectural complexity.

## Core Concepts

### 1. Clean Architecture (Uncle Bob)

**Layers (dependency flows inward):**

- **Entities**: Core business models
- **Use Cases**: Application business rules
- **Interface Adapters**: Controllers, presenters, gateways
- **Frameworks & Drivers**: UI, database, external services

**Key Principles:**

- Dependencies point inward
- Inner layers know nothing about outer layers
- Business logic independent of frameworks
- Testable without UI, database, or external services

### 2. Hexagonal Architecture (Ports and Adapters)

**Components:**

- **Domain Core**: Business logic
- **Ports**: Interfaces defining interactions
- **Adapters**: Implementations of ports (database, REST, message queue)

**Benefits:**

- Swap implementations easily (mock for testing)
- Technology-agnostic core
- Clear separation of concerns

### 3. Domain-Driven Design (DDD)

**Strategic Patterns:**

- **Bounded Contexts**: Separate models for different domains
- **Context Mapping**: How contexts relate
- **Ubiquitous Language**: Shared terminology

**Tactical Patterns:**

- **Entities**: Objects with identity
- **Value Objects**: Immutable objects defined by attributes
- **Aggregates**: Consistency boundaries
- **Repositories**: Data access abstraction
- **Domain Events**: Things that happened

## Clean Architecture Pattern

### Directory Structure

```
app/
├── domain/           # Entities & business rules
│   ├── entities/
│   │   ├── user.py
│   │   └── order.py
│   ├── value_objects/
│   │   ├── email.py
│   │   └── money.py
│   └── interfaces/   # Abstract interfaces
│       ├── user_repository.py
│       └── payment_gateway.py
├── use_cases/        # Application business rules
│   ├── create_user.py
│   ├── process_order.py
│   └── send_notification.py
├── adapters/         # Interface implementations
│   ├── repositories/
│   │   ├── postgres_user_repository.py
│   │   └── redis_cache_repository.py
│   ├── controllers/
│   │   └── user_controller.py
│   └── gateways/
│       ├── stripe_payment_gateway.py
│       └── sendgrid_email_gateway.py
└── infrastructure/   # Framework & external concerns
    ├── database.py
    ├── config.py
    └── logging.py
```

### Implementation Example

```python
# domain/entities/user.py
from dataclasses import dataclass
from datetime import datetime
from typing import Optional

@dataclass
class User:
    """Core user entity - no framework dependencies."""
    id: str
    email: str
    name: str
    created_at: datetime
    is_active: bool = True

    def deactivate(self):
        """Business rule: deactivating user."""
        self.is_active = False

    def can_place_order(self) -> bool:
        """Business rule: active users can order."""
        return self.is_active

# domain/interfaces/user_repository.py
from abc import ABC, abstractmethod
from typing import Optional, List
from domain.entities.user import User

class IUserRepository(ABC):
    """Port: defines contract, no implementation."""

    @abstractmethod
    async def find_by_id(self, user_id: str) -> Optional[User]:
        pass

    @abstractmethod
    async def find_by_email(self, email: str) -> Optional[User]:
        pass

    @abstractmethod
    async def save(self, user: User) -> User:
        pass

    @abstractmethod
    async def delete(self, user_id: str) -> bool:
        pass

# use_cases/create_user.py
from domain.entities.user import User
from domain.interfaces.user_repository import IUserRepository
from dataclasses import dataclass
from datetime import datetime
import uuid

@dataclass
class CreateUserRequest:
    email: str
    name: str

@dataclass
class CreateUserResponse:
    user: User
    success: bool
    error: Optional[str] = None

class CreateUserUseCase:
    """Use case: orchestrates business logic."""

    def __init__(self, user_repository: IUserRepository):
        self.user_repository = user_repository

    async def execute(self, request: CreateUserRequest) -> CreateUserResponse:
        # Business validation
        existing = await self.user_repository.find_by_email(request.email)
        if existing:
            return CreateUserResponse(
                user=None,
                success=False,
                error="Email already exists"
            )

        # Create entity
        user = User(
            id=str(uuid.uuid4()),
            email=request.email,
            name=request.name,
            created_at=datetime.now(),
            is_active=True
        )

        # Persist
        saved_user = await self.user_repository.save(user)

        return CreateUserResponse(
            user=saved_user,
            success=True
        )

# adapters/repositories/postgres_user_repository.py
from domain.interfaces.user_repository import IUserRepository
from domain.entities.user import User
from typing import Optional
import asyncpg

class PostgresUserRepository(IUserRepository):
    """Adapter: PostgreSQL implementation."""

    def __init__(self, pool: asyncpg.Pool):
        self.pool = pool

    async def find_by_id(self, user_id: str) -> Optional[User]:
        async with self.pool.acquire() as conn:
            # Implementation details...
            pass
```

## Resources

- `resources/implementation-playbook.md` for additional detailed patterns, checklists, and templates.

## Limitations

- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.