15 Mistakes I Made as a Django Developer in 6 Years

2026-02-24

15 Mistakes I Made as a Django Developer in 6 Years

When I look back at my early years working with Django, I honestly feel a mix of pride and embarrassment.

Pride because I shipped real systems. Embarrassment because I now see how many things I did the hard way.

Over six years, I have worked on small internal tools, client projects, and large production APIs. Experience helped, but it did not automatically make my architecture good. Most of what I know today came from fixing my own mistakes.

Here are fifteen of them.

1. Putting Too Much Business Logic in Views

In the beginning, my views did everything.

def create_order(request):
    # validation
    # payment logic
    # inventory update
    # email sending
    # logging

It worked. Until it didn't.

The file kept growing. Testing became painful. Reusing logic was almost impossible.

What I learned

Views should coordinate, not decide.
Business rules belong in models or service layers.

Once I started keeping my views thin, everything became easier to test and reason about.

2. Ignoring Database Indexing

I once pushed a feature that filtered millions of rows without adding an index.

Order.objects.filter(status="completed")

On my laptop, it felt fast. In production, it was slow enough to trigger complaints within hours.

What I learned

The database is not magic.
If you frequently filter by a field, index it.
Foreign keys and unique identifiers usually need indexes.

Performance problems often start at the database layer, not in Django.

3. Not Using Transactions Properly

For a long time, I saved objects one after another without thinking about failure.

order.save()
payment.save()

If the payment failed halfway, I ended up with inconsistent data.

What I learned

Wrap related operations in transaction.atomic().

from django.db import transaction

with transaction.atomic():
    order.save()
    payment.save()

Data integrity should not depend on luck.

4. Overusing Signals

Signals felt elegant. Automatic. Clean.

@receiver(post_save, sender=User)
def create_profile(sender, instance, created, **kwargs):

Then debugging started taking hours because logic was happening in places I could not easily trace.

What I learned

Signals are great for decoupled side effects like logging or analytics.
They are terrible for core business logic.

If something is critical to your domain, make it explicit.

5. Mixing Authorization with Business Rules

I used to check permissions deep inside business logic. That created confusion about responsibilities.

What I learned

Authorization belongs at the boundary, such as views or DRF permission classes.
Business rules belong in the domain.

Separating the two makes the codebase cleaner and easier to maintain.

6. Ignoring Query Optimization

I did not fully understand select_related() and prefetch_related() in the early days.

Then I hit the classic N+1 problem.

for order in orders:
    print(order.user.email)

That loop triggered hundreds of queries.

What I learned

Use the ORM properly.

orders = Order.objects.select_related("user")

Understanding how Django talks to the database is not optional if you want to build scalable systems.

7. Writing Fat Serializers in DRF

At one point, my serializers handled validation, business logic, database writes, and side effects.

They became mini applications.

What I learned

Serializers are for validation and representation.
Complex operations should live in services or domain layers.

When serializers stay focused, APIs become easier to evolve.

8. Not Versioning APIs Early

I assumed requirements would stay stable. They did not.

Changing response structures without versioning broke clients.

What I learned

Start with versioning from day one.

/api/v1/

It feels unnecessary at first. It becomes essential later.

9. Treating Django as Just CRUD

For a long time, I thought Django was mostly models, views, and templates.

But Django offers much more. Custom managers. Middleware. Querysets. App modularization.

What I learned

The deeper you understand the framework, the more intentional your architecture becomes.

Django rewards developers who take time to explore its internals.

10. Not Writing Custom Managers

I used to repeat the same filters everywhere.

Order.objects.filter(status="completed", is_deleted=False)

Copy. Paste. Repeat.

What I learned

Encapsulate repeated logic inside managers.

class OrderManager(models.Manager):
    def completed(self):
        return self.filter(status="completed", is_deleted=False)

Order.objects.completed()

Cleaner code. Less duplication. Fewer bugs.

11. Ignoring Idempotency

In payment systems, retrying an endpoint sometimes created duplicate records.

That was painful to fix.

What I learned

Design endpoints to be idempotent.
Store transaction identifiers.
Use unique constraints.

Distributed systems fail in unpredictable ways. Your code should expect retries.

12. Poor Logging Practices

I relied on simple print statements for too long.

print("Error occurred")

When something broke in production, those logs were not helpful.

What I learned

Log meaningful context.
User ID. Request ID. Transaction references. Error details.

Good logging turns production debugging from guessing into investigation.

13. Doing Heavy Work in Request Cycle

I once sent emails synchronously during requests.

send_mail(...)

Users waited. The server stayed busy.

What I learned

Background tasks exist for a reason.
Use workers for email, notifications, and other time-consuming operations.

Keep the request response cycle fast and predictable.

14. Poor App Structure

I created one giant Django app that handled everything.

It worked for a while. Then it became overwhelming.

What I learned

Organize apps around business domains. For example:

users
billing
appointments
notifications

Clear boundaries make scaling the codebase much easier.

15. Postponing Scalability Thinking

I used to say, "We will optimize later."

Later arrived faster than expected.

What I learned

You do not need to over-engineer.
But you should think about caching, database constraints, background processing, and load patterns early.

A little foresight prevents major refactoring.

Final Thoughts

Django itself is not difficult.

Designing good systems is.

Over the years, I realized that framework knowledge is only one part of the equation. Understanding data integrity, separation of concerns, and system design is what truly moves you forward.

If you are early in your Django journey, focus on fundamentals. Learn how databases work. Understand transactions. Study query optimization. Practice clean architecture.

Django will amplify whatever habits you bring into it.

Make sure they are good ones.