← Back to DevBytes

FastAPI vs Django vs FastAPI: Framework Comparison

FastAPI vs Django: A Comprehensive Framework Comparison

Choosing the right Python web framework can shape your entire development experience. Two frameworks dominate the modern conversation: FastAPI and Django. While both let you build web applications in Python, their philosophies, strengths, and ideal use cases differ dramatically. This tutorial walks you through what each framework is, why the comparison matters, practical code examples, and best practices for choosing and using them effectively.

What Is Django?

Django is a batteries-included web framework built for rapid development and clean, pragmatic design. Created in 2005, it follows the Model-View-Template (MVT) architecture and ships with an ORM, authentication system, admin interface, form handling, and more — all out of the box. Django excels at building full-featured, database-backed applications where you need a complete solution without stitching together third-party libraries.

Key characteristics of Django:

Here is a minimal Django application that demonstrates its classic structure:

# models.py - Define your data schema
from django.db import models
from django.contrib.auth.models import User

class Task(models.Model):
    PRIORITY_CHOICES = [
        ('low', 'Low'),
        ('medium', 'Medium'),
        ('high', 'High'),
    ]
    
    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='tasks')
    title = models.CharField(max_length=200)
    description = models.TextField(blank=True)
    priority = models.CharField(max_length=10, choices=PRIORITY_CHOICES, default='medium')
    completed = models.BooleanField(default=False)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    class Meta:
        ordering = ['-created_at']
    
    def __str__(self):
        return self.title

# admin.py - Auto-generated admin interface
from django.contrib import admin
from .models import Task

@admin.register(Task)
class TaskAdmin(admin.ModelAdmin):
    list_display = ['title', 'user', 'priority', 'completed', 'created_at']
    list_filter = ['priority', 'completed']
    search_fields = ['title', 'description']
    list_editable = ['priority', 'completed']

# views.py - Handle requests and return responses
from django.shortcuts import render, redirect, get_object_or_404
from django.contrib.auth.decorators import login_required
from django.http import JsonResponse
from .models import Task

@login_required
def task_list(request):
    tasks = Task.objects.filter(user=request.user)
    context = {'tasks': tasks, 'total_count': tasks.count()}
    return render(request, 'tasks/task_list.html', context)

def task_detail_api(request, task_id):
    task = get_object_or_404(Task, id=task_id, user=request.user)
    return JsonResponse({
        'id': task.id,
        'title': task.title,
        'priority': task.priority,
        'completed': task.completed
    })

# urls.py - Wire up routes
from django.urls import path
from . import views

urlpatterns = [
    path('', views.task_list, name='task_list'),
    path('api//', views.task_detail_api, name='task_detail_api'),
]

Notice how Django handles the ORM, admin registration, authentication decorators, and URL routing in a cohesive, integrated manner. You get immense productivity when building standard web applications.

What Is FastAPI?

FastAPI is a modern, high-performance web framework for building APIs with Python. Released in 2018, it's built on top of Starlette and Pydantic, bringing asynchronous programming, automatic OpenAPI documentation, and type-driven validation to the forefront. FastAPI is purpose-built for APIs — especially real-time, high-concurrency, and microservice architectures.

Key characteristics of FastAPI:

Here is an equivalent task management API built with FastAPI:

# models.py - Pydantic models for validation and serialization
from pydantic import BaseModel, Field
from datetime import datetime
from typing import Optional
from enum import Enum

class Priority(str, Enum):
    low = "low"
    medium = "medium"
    high = "high"

class TaskBase(BaseModel):
    title: str = Field(..., min_length=1, max_length=200, example="Buy groceries")
    description: Optional[str] = Field(None, max_length=1000)
    priority: Priority = Priority.medium
    completed: bool = False

class TaskCreate(TaskBase):
    pass

class TaskResponse(TaskBase):
    id: int
    user_id: int
    created_at: datetime
    updated_at: datetime
    
    model_config = {"from_attributes": True}

class TaskListResponse(BaseModel):
    tasks: list[TaskResponse]
    total_count: int

# database.py - Database setup with SQLAlchemy async
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, relationship
from sqlalchemy import String, Text, DateTime, Boolean, ForeignKey, Enum as SAEnum
from datetime import datetime

DATABASE_URL = "postgresql+asyncpg://user:password@localhost/dbname"
engine = create_async_engine(DATABASE_URL, echo=True)
async_session = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)

class Base(DeclarativeBase):
    pass

class TaskORM(Base):
    __tablename__ = "tasks"
    
    id: Mapped[int] = mapped_column(primary_key=True, index=True)
    user_id: Mapped[int] = mapped_column(ForeignKey("users.id"))
    title: Mapped[str] = mapped_column(String(200))
    description: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
    priority: Mapped[str] = mapped_column(SAEnum(Priority), default=Priority.medium)
    completed: Mapped[bool] = mapped_column(Boolean, default=False)
    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
    updated_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)

# routers/tasks.py - API endpoints with dependency injection
from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy.ext.asyncio import AsyncSession
from typing import List
from . import models, database

router = APIRouter(prefix="/tasks", tags=["tasks"])

async def get_db() -> AsyncSession:
    async with database.async_session() as session:
        yield session

@router.post("/", response_model=models.TaskResponse, status_code=status.HTTP_201_CREATED)
async def create_task(
    task_data: models.TaskCreate,
    db: AsyncSession = Depends(get_db),
    current_user_id: int = Depends(get_current_user)  # Reusable auth dependency
):
    task = database.TaskORM(**task_data.model_dump(), user_id=current_user_id)
    db.add(task)
    await db.commit()
    await db.refresh(task)
    return task

@router.get("/", response_model=models.TaskListResponse)
async def list_tasks(
    db: AsyncSession = Depends(get_db),
    current_user_id: int = Depends(get_current_user),
    priority: Optional[models.Priority] = None,
    completed: Optional[bool] = None
):
    query = select(database.TaskORM).where(database.TaskORM.user_id == current_user_id)
    if priority:
        query = query.where(database.TaskORM.priority == priority)
    if completed is not None:
        query = query.where(database.TaskORM.completed == completed)
    
    result = await db.execute(query)
    tasks = result.scalars().all()
    return {"tasks": tasks, "total_count": len(tasks)}

@router.get("/{task_id}", response_model=models.TaskResponse)
async def get_task(
    task_id: int,
    db: AsyncSession = Depends(get_db),
    current_user_id: int = Depends(get_current_user)
):
    task = await db.get(database.TaskORM, task_id)
    if not task or task.user_id != current_user_id:
        raise HTTPException(status_code=404, detail="Task not found")
    return task

@router.patch("/{task_id}", response_model=models.TaskResponse)
async def update_task(
    task_id: int,
    update_data: models.TaskBase,
    db: AsyncSession = Depends(get_db),
    current_user_id: int = Depends(get_current_user)
):
    task = await db.get(database.TaskORM, task_id)
    if not task or task.user_id != current_user_id:
        raise HTTPException(status_code=404, detail="Task not found")
    
    for field, value in update_data.model_dump(exclude_unset=True).items():
        setattr(task, field, value)
    
    await db.commit()
    await db.refresh(task)
    return task

# main.py - Application entry point
from fastapi import FastAPI
from routers import tasks

app = FastAPI(
    title="Task Management API",
    version="1.0.0",
    description="A high-performance async task management service"
)

app.include_router(tasks.router)

@app.on_event("startup")
async def startup():
    # Initialize database connections, caches, etc.
    pass

The FastAPI version gives you automatic OpenAPI docs at /docs, async database operations, and clean separation of concerns through dependency injection — all while being fully type-checked by your IDE.

Why This Comparison Matters

The choice between Django and FastAPI isn't just about personal preference — it directly impacts your project's performance profile, development speed, scalability, and maintenance burden. Understanding when to use each framework prevents costly architectural mistakes. Here are the key dimensions where the comparison becomes critical:

Detailed Side-by-Side Comparison

Performance & Concurrency

FastAPI runs on ASGI servers like Uvicorn or Hypercorn, enabling asynchronous request handling with event loops. This means a single process can juggle thousands of open connections without blocking. Django's default WSGI server uses a thread/process pool per request, which hits scaling limits faster under I/O-heavy workloads. Django 4.x introduced async view support, but the ORM and much of the ecosystem remain synchronous, limiting the practical benefits.

Benchmark comparison for a simple JSON endpoint (requests per second):

# FastAPI with Uvicorn (single worker)
# ~15,000 req/s for simple async endpoint

# Django with Gunicorn (4 workers, sync)
# ~4,000 req/s for equivalent view

# Django with Gunicorn + gevent (patched)
# ~8,000 req/s — better, but not native async

For WebSocket-heavy applications, FastAPI's native support is a clear advantage:

# FastAPI WebSocket example
from fastapi import FastAPI, WebSocket, WebSocketDisconnect

app = FastAPI()
active_connections: list[WebSocket] = []

@app.websocket("/ws/{client_id}")
async def websocket_endpoint(websocket: WebSocket, client_id: str):
    await websocket.accept()
    active_connections.append(websocket)
    try:
        while True:
            data = await websocket.receive_text()
            # Broadcast to all connected clients
            for connection in active_connections:
                await connection.send_text(f"Client {client_id}: {data}")
    except WebSocketDisconnect:
        active_connections.remove(websocket)

Database & ORM

Django's ORM is arguably its strongest feature. It provides automatic migration generation, a rich query API, model inheritance, and seamless integration with the admin panel. FastAPI doesn't prescribe an ORM — you choose SQLAlchemy, Tortoise, Prisma, or raw queries. This gives flexibility but requires more setup.

Django ORM query — expressive and concise:

# Complex queries with Django ORM
from django.db.models import Count, Q, Avg

high_priority_completed = Task.objects.filter(
    Q(priority='high') & Q(completed=True)
).select_related('user').only('title', 'user__username')

task_stats = Task.objects.values('priority').annotate(
    count=Count('id'),
    avg_completion_time=Avg('updated_at') - Avg('created_at')
)

Equivalent with SQLAlchemy async:

# SQLAlchemy async equivalent
from sqlalchemy import select, func
from sqlalchemy.orm import selectinload

stmt = (
    select(TaskORM)
    .where(TaskORM.priority == 'high', TaskORM.completed == True)
    .options(selectinload(TaskORM.user))
    .with_only_columns(TaskORM.title, UserORM.username)
)
result = await db.execute(stmt)
tasks = result.all()

# Aggregation query
stmt = (
    select(
        TaskORM.priority,
        func.count(TaskORM.id).label('count'),
    )
    .group_by(TaskORM.priority)
)
result = await db.execute(stmt)
stats = result.all()

Authentication & Security

Django ships with a complete authentication system — user models, session management, password hashing, permissions, groups, and CSRF protection. You get login_required decorators, AuthenticationForm, and UserAdmin right away.

# Django built-in auth
from django.contrib.auth import authenticate, login, logout
from django.contrib.auth.decorators import login_required, permission_required
from django.contrib.auth.models import User, Group, Permission

@login_required
@permission_required('tasks.can_manage_tasks', raise_exception=True)
def manage_tasks(request):
    # Only authenticated users with specific permissions reach here
    user_tasks = Task.objects.filter(user=request.user)
    return render(request, 'manage.html', {'tasks': user_tasks})

# Login view with built-in form handling
from django.contrib.auth.forms import AuthenticationForm

def login_view(request):
    if request.method == 'POST':
        form = AuthenticationForm(request, data=request.POST)
        if form.is_valid():
            user = form.get_user()
            login(request, user)
            return redirect('dashboard')
    else:
        form = AuthenticationForm()
    return render(request, 'login.html', {'form': form})

FastAPI requires you to build authentication yourself, but offers elegant dependency injection to keep it clean and reusable:

# FastAPI JWT authentication with dependency injection
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from datetime import datetime, timedelta

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")
SECRET_KEY = "your-secret-key"
ALGORITHM = "HS256"

async def get_current_user(
    token: str = Depends(oauth2_scheme),
    db: AsyncSession = Depends(get_db)
) -> UserORM:
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        user_id: int = payload.get("sub")
        if user_id is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
    
    user = await db.get(UserORM, user_id)
    if user is None:
        raise credentials_exception
    return user

# Use the dependency in any route — clean and composable
@router.get("/me")
async def read_current_user(current_user: UserORM = Depends(get_current_user)):
    return {"user_id": current_user.id, "email": current_user.email}

# Permission checking as a dependency factory
def require_permission(permission_name: str):
    async def permission_checker(
        current_user: UserORM = Depends(get_current_user),
        db: AsyncSession = Depends(get_db)
    ) -> bool:
        has_permission = await check_user_permission(db, current_user, permission_name)
        if not has_permission:
            raise HTTPException(status_code=403, detail="Insufficient permissions")
        return True
    return permission_checker

@router.delete("/{task_id}", dependencies=[Depends(require_permission("tasks.delete"))])
async def delete_task(task_id: int, db: AsyncSession = Depends(get_db)):
    # Permission checked automatically via dependencies
    pass

Documentation & Developer Experience

FastAPI automatically generates interactive API documentation from your Pydantic models and route annotations. Visit /docs for Swagger UI or /redoc for ReDoc. Django requires third-party packages like drf-spectacular or drf-yasg (with Django REST Framework) to achieve similar results, and the setup is more verbose.

FastAPI also gives you editor autocompletion and type checking across your entire codebase thanks to Pydantic and type hints — Django's dynamic querysets and template rendering don't offer the same static analysis benefits.

When to Choose Django

When to Choose FastAPI

Best Practices for Framework Selection and Usage

1. Avoid Framework Coupling in Your Business Logic

Keep your core business logic framework-agnostic. This makes it easier to migrate between frameworks or use both in different parts of your system:

# core/services.py - Framework-independent business logic
from dataclasses import dataclass
from typing import Optional

@dataclass
class TaskService:
    """Pure business logic with no framework dependencies."""
    
    @staticmethod
    def can_complete_task(task_priority: str, task_completed: bool) -> bool:
        """Business rule: high-priority tasks require manager approval."""
        if task_priority == 'high' and not task_completed:
            return False  # Requires special workflow
        return True
    
    @staticmethod
    def calculate_priority_score(title_length: int, has_description: bool) -> float:
        """Heuristic for automatic priority suggestion."""
        base_score = min(title_length / 100, 1.0) * 0.5
        description_bonus = 0.5 if has_description else 0.0
        return base_score + description_bonus

# Used in Django view
def complete_task_view(request, task_id):
    task = get_object_or_404(Task, id=task_id)
    if TaskService.can_complete_task(task.priority, task.completed):
        task.completed = True
        task.save()
    return redirect('task_list')

# Used in FastAPI endpoint
@router.post("/{task_id}/complete")
async def complete_task_endpoint(task_id: int, db: AsyncSession = Depends(get_db)):
    task = await db.get(TaskORM, task_id)
    if TaskService.can_complete_task(task.priority, task.completed):
        task.completed = True
        await db.commit()
    return {"status": "updated"}

2. Use Django REST Framework for Django APIs

If you need a robust API within a Django project, Django REST Framework (DRF) provides serializers, viewsets, routers, and authentication classes that rival FastAPI's developer experience — though with more boilerplate:

# Django REST Framework serializer and viewset
from rest_framework import viewsets, serializers, permissions
from rest_framework.decorators import action
from rest_framework.response import Response

class TaskSerializer(serializers.ModelSerializer):
    days_since_created = serializers.SerializerMethodField()
    
    class Meta:
        model = Task
        fields = ['id', 'title', 'priority', 'completed', 'days_since_created']
    
    def get_days_since_created(self, obj):
        return (datetime.now().date() - obj.created_at.date()).days

class TaskViewSet(viewsets.ModelViewSet):
    serializer_class = TaskSerializer
    permission_classes = [permissions.IsAuthenticated]
    
    def get_queryset(self):
        return Task.objects.filter(user=self.request.user)
    
    @action(detail=True, methods=['post'])
    def toggle_complete(self, request, pk=None):
        task = self.get_object()
        task.completed = not task.completed
        task.save()
        return Response({'completed': task.completed})

3. Structure FastAPI Projects Like Django Apps

FastAPI doesn't enforce project structure, which can lead to messy codebases. Adopt a modular structure inspired by Django's app system:

project/
├── main.py                 # FastAPI app instance, include routers
├── core/
│   ├── config.py           # Settings, environment variables
│   ├── security.py         # Auth dependencies, JWT handling
│   └── database.py         # Engine, session factory, Base class
├── apps/
│   ├── tasks/
│   │   ├── models.py       # Pydantic schemas
│   │   ├── orm.py          # SQLAlchemy ORM models
│   │   ├── router.py       # API endpoints
│   │   ├── service.py      # Business logic
│   │   └── dependencies.py # App-specific dependencies
│   └── users/
│       ├── models.py
│       ├── orm.py
│       ├── router.py
│       └── service.py
├── tests/
│   ├── conftest.py         # Shared fixtures, test database
│   ├── test_tasks.py
│   └── test_users.py
└── alembic/                # Database migrations
    └── versions/

4. Leverage Async Only Where It Matters

Not every endpoint benefits from async. Database queries, external API calls, and file I/O gain the most. CPU-bound operations can block the event loop. Use run_in_threadpool for CPU-heavy work in FastAPI:

from fastapi.concurrency import run_in_threadpool
import pandas as pd

@app.get("/reports/generate")
async def generate_report(user_id: int, db: AsyncSession = Depends(get_db)):
    # Fetch data async
    tasks = await db.execute(select(TaskORM).where(TaskORM.user_id == user_id))
    task_data = tasks.scalars().all()
    
    # CPU-heavy pandas processing in threadpool to avoid blocking event loop
    result = await run_in_threadpool(
        lambda: pd.DataFrame([t.__dict__ for t in task_data]).describe().to_dict()
    )
    
    return result

5. Test Both Frameworks Thoroughly

Django provides a powerful test client and fixtures system. FastAPI relies on Starlette's TestClient and async test support:

# FastAPI async testing with pytest
import pytest
from httpx import AsyncClient
from main import app
from core.database import engine, Base

@pytest.fixture(scope="session")
async def test_db():
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
    yield
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.drop_all)

@pytest.mark.asyncio
async def test_create_task(test_db):
    async with AsyncClient(app=app, base_url="http://test") as client:
        response = await client.post(
            "/tasks/",
            json={"title": "Test task", "priority": "high"},
            headers={"Authorization": "Bearer test_token"}
        )
    assert response.status_code == 201
    assert response.json()["title"] == "Test task"
    assert response.json()["priority"] == "high"

# Django testing with built-in TestCase
from django.test import TestCase, Client
from django.contrib.auth.models import User

class TaskTestCase(TestCase):
    def setUp(self):
        self.user = User.objects.create_user(username='testuser', password='secret')
        self.client = Client()
        self.client.login(username='testuser', password='secret')
    
    def test_task_creation(self):
        response = self.client.post('/tasks/create/', {
            'title': 'Test task',
            'priority': 'high'
        })
        self.assertEqual(response.status_code, 302)  # Redirect on success
        self.assertTrue(Task.objects.filter(title='Test task').exists())

6. Consider Using Both Frameworks Together

Many production systems combine Django and FastAPI. A common pattern is Django handling the admin, ORM, and server-rendered pages, while FastAPI serves as a high-performance API layer using the same database models:

# Shared Django ORM models used by FastAPI
# django_app/models.py
from django.db import models

class Product(models.Model):
    sku = models.CharField(max_length=50, unique=True)
    name = models.CharField(max_length=200)
    price = models.DecimalField(max_digits=10, decimal_places=2)

# fastapi_service/main.py
import django
import os
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'django_app.settings')
django.setup()

from fastapi import FastAPI
from django_app.models import Product
from asgiref.sync import sync_to_async

app = FastAPI()

@app.get("/products/{sku}")
async def get_product(sku: str):
    # Use Django ORM with sync_to_async for async compatibility
    product = await sync_to_async(Product.objects.get)(sku=sku)
    return {"sku": product.sku, "name": product.name, "price": float(product.price)}

@app.get("/products")
async def list_products(min_price: float = 0):
    products = await sync_to_async(list)(Product.objects.filter(price__gte=min_price))
    return [{"sku": p.sku, "name": p.name, "price": float(p.price)} for p in products]

This hybrid approach lets you leverage Django's admin and ORM maturity while gaining FastAPI's async performance and auto-documentation for your API endpoints.

Migration Considerations

If you're migrating from Django to FastAPI (or vice versa), do it incrementally:

Conclusion

Django and FastAPI represent two different philosophies in Python web development. Django offers a complete, integrated ecosystem where you get immense productivity for building full-featured web applications — admin panels, authentication, ORM, and templates all work together seamlessly. FastAPI delivers raw performance, modern async capabilities, and type-driven development that shines for APIs, microservices, and real-time applications.

Neither framework is universally superior. The right choice depends on your specific requirements around performance, development speed, team composition, and architectural goals. Many successful projects use Django for the backend admin and server-rendered pages while running FastAPI for high-throughput API endpoints — proving that the best solution is often a pragmatic combination of both. Whichever you choose, keeping your business logic framework-agnostic, structuring your code cleanly, and writing comprehensive tests will ensure your application remains maintainable and adaptable as your needs evolve.

🚀 Need a reliable AI agent for your project?

Deploy Hermes Agent in 10 minutes. Managed hosting, zero DevOps.

Get Started — $23.99/mo
← Back to all articles