PROFESSIONAL DJANGO ENGINEERING SERIES #5 100 orders. A loop. A template that accesses order.user.email. Result: 701 database queries. Here is how it happens — and how to fix it in one line. The N+1 query problem is the most common performance issue in Django applications. It is also the most invisible one in development, because your local database has twenty records. It only becomes visible in production, where it has twenty thousand — and by then, it is an incident. The ORM does not hide SQL from you. It writes SQL for you. Understanding what SQL it writes — and why — is what separates ORM users from ORM professionals. How N+1 Happens Here is a view that looks perfectly innocent: # views.py — looks clean, causes disaster at scale def order_list ( request ): orders = Order . objects .…