Low-level caching with Rails.cache - Mini Project: Build & Apply

Low-level caching with Rails.cache

📖 Scenario: You are building a simple Rails app that fetches and displays product prices. To make the app faster, you want to store the prices temporarily in a cache so the app doesn't have to fetch them every time.

🎯 Goal: Build a small Rails code snippet that uses Rails.cache to store and retrieve product prices, improving speed by avoiding repeated calculations.

📋 What You'll Learn

Create a hash called product_prices with exact product-price pairs

Create a variable called cache_key with the value "product_prices_cache"

Use Rails.cache.fetch with cache_key to store product_prices if not cached

Add an expiration time of 5 minutes to the cache fetch

💡 Why This Matters

🌍 Real World

Caching is used in web apps to speed up repeated data access by storing results temporarily.

💼 Career

Understanding Rails low-level caching helps backend developers optimize app performance and reduce database load.

1

Create the product prices hash

Create a hash called product_prices with these exact entries: "apple" => 100, "banana" => 50, "orange" => 75.

Ruby on Rails

# Create the product_prices hash with exact entries
# Your code here

Need a hint?

Use Ruby hash syntax with string keys and integer values.

2

Set the cache key

Create a variable called cache_key and set it to the string "product_prices_cache".

Ruby on Rails

product_prices = { "apple" => 100, "banana" => 50, "orange" => 75 }
# Create cache_key variable with value "product_prices_cache"
# Your code here

Need a hint?

Just assign the string to the variable.

3

Fetch or store product prices in cache

Use Rails.cache.fetch with cache_key to get the cached product prices. If the cache is empty, store product_prices in the cache.

Ruby on Rails

product_prices = { "apple" => 100, "banana" => 50, "orange" => 75 }
cache_key = "product_prices_cache"
# Use Rails.cache.fetch with cache_key to cache product_prices
# Your code here

Need a hint?

Use a block with Rails.cache.fetch to provide the value if cache is empty.

4

Add expiration time to cache fetch

Modify the Rails.cache.fetch call to add an expiration time of 5 minutes using the expires_in option.

Ruby on Rails

product_prices = { "apple" => 100, "banana" => 50, "orange" => 75 }
cache_key = "product_prices_cache"
cached_prices = Rails.cache.fetch(cache_key) { product_prices }
# Add expires_in: 5.minutes option to Rails.cache.fetch
# Your code here

Need a hint?

Pass expires_in: 5.minutes as a second argument to Rails.cache.fetch.