Caching

Django · Reference cheat sheet

📋 Overview

Django’s cache framework stores expensive results (pages, fragments, query results) behind a pluggable backend: local memory, Memcached, Redis, database, or file. Configure CACHES, then use the low-level API, per-view decorators, or template fragment caching.

🔧 Core concepts

Backends: LocMemCache (dev), RedisCache (Django 4.0+), Memcached, DB, file.

💡 Examples

Settings (Redis):

CACHES = {
    "default": {
        "BACKEND": "django.core.cache.backends.redis.RedisCache",
        "LOCATION": "redis://127.0.0.1:6379/1",
        "KEY_PREFIX": "myapp",
        "TIMEOUT": 300,
    }
}

Low-level:

from django.core.cache import cache

def get_article(slug: str):
    key = f"article:{slug}"
    article = cache.get(key)
    if article is None:
        article = Article.objects.select_related("author").get(slug=slug)
        cache.set(key, article, timeout=60 * 10)
    return article

View + template fragment:

from django.views.decorators.cache import cache_page

@cache_page(60 * 15)
def homepage(request):
    ...

{% load cache %}
{% cache 500 sidebar request.user.pk %}
  ... expensive ...
{% endcache %}

⚠️ Pitfalls

• Caching personalized pages without varying on user/session → data leaks.
• LocMemCache is per-process—wrong for multi-worker production.
• Stale cache after writes—invalidate keys in signals/services.
• Pickling large querysets—cache IDs or rendered HTML instead.
• Forgetting KEY_PREFIX when sharing Redis across apps.

🔗 Related

• Settings
• Signals
• Templates
• Sessions
• Middleware