Page and action caching in Ruby on Rails - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when a cached page is expired in Rails page caching?

Consider a Rails app using page caching. When the cached page is expired, what is the next behavior when a user requests that page?

A Rails serves the stale cached page until the cache is manually refreshed.

B Rails redirects the user to the homepage automatically.

C Rails returns a 404 error because the cached page is missing.

D Rails regenerates the page by running the controller action and updates the cache before serving.

💡 Hint

Think about how caching helps serve fresh content after expiration.

When a cached page expires, Rails runs the controller action again to regenerate the page and updates the cache. This ensures users get fresh content.

📝 Syntax

intermediate

Which code snippet correctly enables action caching in a Rails controller?

Identify the correct way to enable action caching for the show action in a Rails controller.

A caches_page :show

B cache_action :show

C caches_action :show

D cache_page :show

💡 Hint

Look for the exact Rails method name for action caching.

The correct method to enable action caching is caches_action. The others are either misspelled or relate to page caching.

🔧 Debug

advanced

Why does the cached page not update after data changes in Rails page caching?

A Rails app uses page caching, but after updating the database, the cached page still shows old data. What is the most likely cause?

A The cache was not expired or deleted after the data update.

B The controller action is missing the <code>caches_action</code> call.

C The view template has syntax errors preventing cache refresh.

D The server is running in development mode, which disables caching.

💡 Hint

Think about what triggers cache refresh in page caching.

Page caching serves static files. If the cache is not expired or deleted after data changes, the old cached page remains served.

🧠 Conceptual

advanced

What is a key difference between page caching and action caching in Rails?

Choose the statement that best describes a fundamental difference between page caching and action caching.

A Page caching stores the entire response as a static file, bypassing Rails, while action caching runs filters before serving cached content.

B Action caching stores static files on disk, while page caching caches only controller variables.

C Page caching requires database queries on every request, action caching does not.

D Action caching is faster because it skips the controller entirely.

💡 Hint

Consider how each caching type interacts with the Rails stack.

Page caching saves the full HTML as a static file served directly by the web server, skipping Rails. Action caching still runs controller filters before serving cached content.

❓ state_output

expert

What is the output after running this Rails action caching code snippet?

Given the following Rails controller snippet with action caching enabled, what will be the value of @count after two consecutive requests?

Ruby on Rails

class ItemsController < ApplicationController
  caches_action :index

  def index
    @count ||= 0
    @count += 1
    render plain: "Count: #{@count}"
  end
end

A "Count: 1" on first request, "Count: 2" on second request

B "Count: 1" on first request, "Count: 1" on second request

C "Count: 0" on first request, "Count: 1" on second request

D "Count: 2" on first request, "Count: 3" on second request

💡 Hint

Remember how action caching serves cached content without rerunning the action.

Action caching caches the entire response after the first request. The controller action does not run on the second request, so @count stays at 1.