Fragment caching in Ruby on Rails - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is fragment caching in Rails?

Fragment caching stores parts of a view to speed up page rendering by reusing cached HTML instead of regenerating it every time.

beginner

How do you create a fragment cache block in a Rails view?

Use cache do ... end around the HTML you want to cache in the view template.

beginner

Why is fragment caching useful in a web app?

It reduces server work by reusing parts of pages that don’t change often, making pages load faster for users.

intermediate

How can you expire a fragment cache in Rails?

You can expire it by changing the cache key or using methods like expire_fragment in controllers or background jobs.

intermediate

What is a cache key in fragment caching?

A cache key is a unique identifier for the cached fragment, often based on model data or timestamps to keep cache fresh.

Which Rails helper is used to wrap content for fragment caching?

A cache do ... end

B render partial

C content_for

D link_to

The cache do ... end helper wraps the content you want to cache as a fragment.

What happens if the cache key changes for a fragment cache?

A The server crashes

B The cached fragment is ignored and regenerated

C The cache is deleted permanently

D Nothing, cache stays the same

Changing the cache key forces Rails to regenerate the cached fragment with new content.

Fragment caching is best used when:

A Parts of the page rarely change

B Every part of the page changes every request

C You want to cache the entire page

D You want to cache database queries

Fragment caching speeds up rendering by caching parts that don’t change often.

Which method can be used to manually expire a fragment cache in Rails?

A clear_cache

B delete_cache

C reset_cache

D expire_fragment

The expire_fragment method removes a cached fragment so it can be regenerated.

What is a common way to generate a cache key for a fragment?

A Using current time only

B Using random numbers

C Using model id and updated_at timestamp

D Using user IP address

Using model id and updated_at timestamp ensures cache updates when data changes.

Explain how fragment caching works in Rails and why it improves performance.

Think about saving time by reusing parts that don’t change.

Describe how to implement and expire a fragment cache in a Rails view and controller.

Focus on how to wrap content and how to clear or update the cache.