Why caching improves response times in Ruby on Rails - See It in Action

Why caching improves response times

📖 Scenario: You are building a simple Rails web app that shows a list of popular books. Each time a user visits the page, the app fetches the book data from a slow external source. To make the page load faster, you want to use caching.

🎯 Goal: Build a Rails controller that caches the list of books so that repeated visits load the page faster by avoiding repeated slow data fetching.

📋 What You'll Learn

Create a controller action that fetches book data

Add a cache key variable to control caching

Use Rails caching to store and retrieve the book list

Render the cached book list in the response

💡 Why This Matters

🌍 Real World

Caching is used in web apps to speed up response times by saving results of slow operations like database queries or API calls.

💼 Career

Understanding caching is important for backend developers to improve app performance and user experience.

1

Set up the books data method

In the BooksController, create a method called fetch_books that returns an array of these exact book titles: ["The Hobbit", "1984", "Pride and Prejudice"].

Ruby on Rails

class BooksController < ApplicationController
  # Create fetch_books method returning the exact array
  # Your code here
end

Need a hint?

Define a method named fetch_books inside BooksController that returns the array exactly as shown.

2

Add a cache key variable

Inside BooksController, add a private method called cache_key that returns the string "books_list_v1".

Ruby on Rails

class BooksController < ApplicationController
  def fetch_books
    ["The Hobbit", "1984", "Pride and Prejudice"]
  end

  # Add private cache_key method returning "books_list_v1"
  # Your code here
end

Need a hint?

Create a private method named cache_key that returns the string exactly as shown.

3

Use Rails caching to store and fetch books

Add an action called index in BooksController that uses Rails.cache.fetch(cache_key) to store or retrieve the books by calling fetch_books. Assign the result to @books.

Ruby on Rails

class BooksController < ApplicationController
  def fetch_books
    ["The Hobbit", "1984", "Pride and Prejudice"]
  end

  def index
    # Use Rails.cache.fetch with cache_key to assign @books
    # Your code here
  end

  private

  def cache_key
    "books_list_v1"
  end
end

Need a hint?

Define index method that sets @books using Rails.cache.fetch(cache_key) with a block calling fetch_books.

4

Render the cached books list

In the index action, add a line to render the @books array as JSON using render json: @books.

Ruby on Rails

class BooksController < ApplicationController
  def fetch_books
    ["The Hobbit", "1984", "Pride and Prejudice"]
  end

  def index
    @books = Rails.cache.fetch(cache_key) do
      fetch_books
    end
    # Render @books as JSON
    # Your code here
  end

  private

  def cache_key
    "books_list_v1"
  end
end

Need a hint?

Add render json: @books inside the index method to send the cached books as JSON response.