Cache invalidation strategies in Django - Mini Project: Build & Apply

Cache Invalidation Strategies in Django

📖 Scenario: You are building a Django web application that shows a list of products. To improve performance, you want to cache the product list page. However, when products change, the cache must be invalidated so users see fresh data.

🎯 Goal: Build a simple Django view that caches the product list page and invalidates the cache when a product is updated.

📋 What You'll Learn

Create a dictionary called products with three products and their prices.

Create a variable called cache_timeout and set it to 300 seconds.

Write a Django view function called product_list that caches the product list page using cache.get and cache.set.

Add a function called invalidate_cache that deletes the cached product list when a product is updated.

💡 Why This Matters

🌍 Real World

Caching is used in web apps to speed up page loading by storing data temporarily. Cache invalidation ensures users see updated information after changes.

💼 Career

Understanding cache invalidation is important for backend developers working with Django or any web framework to build fast and reliable applications.

1

Create the initial product data

Create a dictionary called products with these exact entries: 'apple': 1.2, 'banana': 0.5, 'cherry': 2.5.

Django

# Create the products dictionary with exact entries
# Your code here

Need a hint?

Use curly braces to create a dictionary with the exact keys and values.

2

Set the cache timeout duration

Create a variable called cache_timeout and set it to 300 (seconds).

Django

products = {'apple': 1.2, 'banana': 0.5, 'cherry': 2.5}
# Set cache_timeout to 300 seconds
# Your code here

Need a hint?

Just assign the number 300 to the variable cache_timeout.

3

Create the cached product list view

Write a Django view function called product_list that uses cache.get('product_list') to get cached data. If cache is empty, create a string listing products and prices, then store it with cache.set('product_list', product_data, cache_timeout). Return the product data string.

Django

products = {'apple': 1.2, 'banana': 0.5, 'cherry': 2.5}
cache_timeout = 300
from django.core.cache import cache

def product_list(request):
    # Your code here

Need a hint?

Use cache.get to check cache, build the string if missing, then use cache.set to save it.

4

Add cache invalidation function

Add a function called invalidate_cache that calls cache.delete('product_list') to remove the cached product list when a product is updated.

Django

products = {'apple': 1.2, 'banana': 0.5, 'cherry': 2.5}
cache_timeout = 300
from django.core.cache import cache

def product_list(request):
    product_data = cache.get('product_list')
    if product_data is None:
        product_data = '\n'.join(f"{name}: ${price}" for name, price in products.items())
        cache.set('product_list', product_data, cache_timeout)
    return product_data

def invalidate_cache():
    # Your code here

Need a hint?

Use cache.delete with the same cache key to remove cached data.