Django scales beautifully when you follow the right patterns from day one. This article covers the architectural decisions that prevent technical debt from accumulating as your project grows.
Keep each Django app focused on a single domain. An app called 'users' should only contain user-related models, views, and business logic. Cross-cutting concerns like permissions or notifications belong in their own apps.
Introduce a service layer between views and models. Views should do nothing more than validate input, call a service function, and return a response. Services contain the business logic and are easy to test without a request context.
Use select_related and prefetch_related consistently to avoid N+1 query problems. Install Django Debug Toolbar in development and review SQL queries for every new feature. A single page should rarely need more than 10 database queries.
For background tasks, integrate Celery with Redis or use Django-Q. Keep tasks idempotent so they can safely retry after failure. Log every task execution with its inputs and result.