Building Clean Architecture in Django: How OOP, SOLID, and Design Patterns Keep Your Code Scalable

Django is one of the most popular web frameworks for Python, and it comes with batteries included. However, many Django projects often become fat views and models, making them difficult to maintain in the long run.

To build a project that is scalable, testable, and maintainable, we can borrow ideas from Object-Oriented Programming (OOP), SOLID principles, and design patterns.

In this article, we’ll walk through how we structured a Clean Architecture in Django project with repositories, services, strategies, and clean architecture layers to keep business logic organized and future-proof.

Why Traditional Django Apps Get Messy

A typical Django app tends to mix responsibilities:

• • Models often include too much business logic.
• • Views handle both request/response formatting and core application logic.
• • Serializers may start validating and even triggering business workflows.

This violates the Single Responsibility Principle (SRP) and makes testing harder.

To solve this, we restructure our Django app into layers, the foundation of Clean Architecture in Django.

Layered Architecture for Django

We divide responsibilities into four main layers:

• • Models (Entities) → Represent core business data (Referral, Hospital, etc.).
• • Repositories → Handle persistence (CRUD operations via ORM).
• • Services → Contain business rules and orchestrate workflows.
• • Views (APIs) → Handle HTTP requests/responses only, delegating logic to services.

This separation makes it easy to swap database engines, change business logic, or add external integrations without rewriting everything. Such separation is a key part of Clean Architecture in Django.

Enhancing Models with OOP

Instead of using plain Django models, we extended them with OOP features:

class Referral(BaseModel):
name = models.CharField(max_length=100)
email = models.EmailField(unique=True)
phone = models.CharField(max_length=15, null=True, blank=True)
referral_code = models.CharField(max_length=20, unique=True)
is_active = models.BooleanField(default=True)

@property
def display_name(self):
return f"Referral: {self.name} ({self.email})"

def activate(self):
self.is_active = True
self.save()

Here, we use:

• • Encapsulation defines business methods such as activate() and deactivate() within the model.
• • Validation and cloning via a reusable Base Model.
• • Domain-driven design where models represent real-world behavior.

Repository Pattern in Django

We created a Base Repository for reusable CRUD logic:

class BaseRepository(Generic[T, ID]):
def create(self, **kwargs) -> T:
return self.model.objects.create(**kwargs)

def get_by_id(self, entity_id: ID) -> Optional[T]:
return self.model.objects.filter(id=entity_id).first()

Then, we built Referral Repository:

class ReferralRepository(BaseRepository[Referral, int]):
model = Referral

def get_by_email(self, email: str) -> Optional[Referral]:
return self.model.objects.filter(email=email).first()

def get_active_referrals(self) -> List[Referral]:
return list(self.model.objects.filter(is_active=True))

This isolates database operations, making business logic independent of Django ORM, a crucial part of implementing Clean Architecture in Django.

Service Layer with DIP and Strategy Pattern

Our Referral Service consumes the repository and applies business rules:

class ReferralService:
def __init__(self, user, bonus_strategy=None, notification_service=None):
self.repo = ReferralRepository()
self.bonus_strategy = bonus_strategy
self.notification_service = notification_service

def create_referral(self, data):
referral = self.repo.create(**data)
bonus = self.bonus_strategy.apply(referral) if self.bonus_strategy else None
if self.notification_service:
self.notification_service.send_referral_created(referral)
return referral, bonus

Here we used:

• • Dependency Inversion Principle (DIP) → Referral Service depends on abstractions (bonus_strategy, notification_service), not implementations.
• • Strategy Pattern → Different bonus calculation strategies can be plugged in without changing service code.
• • SRP → Service only manages business rules, not persistence.

This abstraction aligns with the Clean Architecture in Django philosophy, where each component has a clear, single responsibility.

API Views – Keeping Them Thin

Instead of bloating views with logic, we delegate to services:

class ReferralCreateAPIView(CreateAPIView):
serializer_class = ReferralSerializer

def perform_create(self, serializer):
service = ReferralService(
user=self.request.user,
bonus_strategy=SignUpBonusStrategy(),
notification_service=EmailNotificationService()
)
referral, bonus = service.create_referral(serializer.validated_data)
return referral

Now the view only:

• • Validates input with a serializer.
• • Calls the service for logic.
• • Returns the response.

This structure exemplifies Clean Architecture in Django, keeping presentation separate from business logic.

Benefits of This Approach

Maintainability: Business logic is centralized in services, not scattered in views.
Testability: Each layer (repository, service, strategy) can be unit-tested in isolation.
Extensibility: New business rules can be added without rewriting APIs.
OOP-friendly: Models encapsulate behavior, not just data.
SOLID-compliant: Separation of concerns + dependency inversion.

All these benefits are outcomes of applying Clean Architecture in Django principles to real-world projects.