I found an interesting N+1 problem in a Django application...

Bun Rong — Sun, 13 Sep 2026 10:33:24 +0000

I recently found an interesting N+1 query problem in a Django application.

The code looked completely normal:

orders = Order.objects.all()

for order in orders:
    print(order.customer.name)

But Django was actually doing something like:

1 query  → fetch all orders
+ N queries → fetch each customer's data
----------------------------------------
101 queries for 100 orders 😬

The fix was simple:

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

Now Django can fetch the related customer data in the same query instead of querying the database for every order.

The interesting part isn't just knowing select_related().

The real challenge is finding where the N+1 queries are happening, especially when they come from serializers, templates, nested relationships, or code you didn't realize was triggering additional database queries.

I wrote a practical walkthrough covering how to detect N+1 queries in Django, measure the queries, and fix them with select_related(), prefetch_related(), and assertNumQueries().

👉 Read the full article:

How to Find and Fix N+1 Queries in Django — Rong

A practical guide to finding N+1 query problems in Django with django-debug-toolbar and assertNumQueries, and fixing them with select_related, prefetch_related and Prefetch.

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I found an interesting N+1 problem in a Django application...

How to Find and Fix N+1 Queries in Django — Rong