How do transactions work in Django?
Django transactions group database operations so partial writes do not persist when an error happens mid-flow.
- Use transaction.atomic
- Good for multi-step writes
- Keep the transaction scope tight
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How do you avoid N+1 queries in Django?
Use relation-aware loading like select_related and prefetch_related when templates or loops will touch related objects repeatedly.
- Spot repeated per-row queries
- Load related data intentionally
- Profile before guessing
How does authentication differ from authorization in Django?
Authentication verifies who the user is, while authorization decides what that user is allowed to do.
- Login proves identity
- Permissions control access
- Both matter for secure apps
select_related vs prefetch_related
select_related joins single-valued relations in SQL; prefetch_related fetches related collections in extra queries.
- select_related for FK and O2O
- prefetch_related for M2M and reverse FK
- Both reduce N+1 queries
Session vs cookie in Django
Cookies live in the browser, while sessions usually store server-side state and use a cookie only for the session key.
- Cookie stores small client data
- Session stores server data
- Secure cookies still live client-side
Static files vs media files in Django
Static files are app assets you ship, while media files are user-uploaded content created after deployment.
- Static belongs to the codebase or build output
- Media is runtime content
- Storage and serving patterns often differ
What are Django model managers and QuerySet methods?
Managers and custom QuerySet methods let you package reusable query logic close to the model layer.
- Keeps query rules centralized
- Improves readability
- Good for domain-specific filters
What is a custom user model in Django and when should you use one?
A custom user model lets you control user fields and authentication structure instead of being locked into the default user shape.
- Best decided at project start
- Helps avoid future auth migration pain
- Use AUTH_USER_MODEL consistently
What is collectstatic in Django?
collectstatic gathers static assets into one deployable location for serving in production.
- Used before deployment
- Combines assets from apps
- Often paired with CDN or object storage
What is CSRF in Django?
CSRF protection ensures a state-changing request comes from your site and includes a valid token.
- Protects POST and unsafe methods
- Relies on token validation
- Use csrf_token in forms
What is database migration squashing in Django?
Migration squashing combines many historical migrations into a smaller set to reduce noise and startup cost.
- Good for mature apps
- Keep history manageable
- Needs care when teams still depend on old migration paths
What is Django admin useful for?
Django admin gives a fast internal CRUD interface for managing data models without building custom screens first.
- Great for internal tooling
- Good for content editing and ops workflows
- Usually not the public product UI