Ruby on Rails Interview Prep: Key Questions to Expect in Your Interview

Ruby on Rails is a powerful web application framework that simplifies the development process. If you’re preparing for a role that involves Ruby on Rails, expect questions that test your understanding of MVC architecture, Rails conventions, and database integrations. To help you prepare, here’s a list of frequently asked questions that you might encounter during your interview.

Basic Questions

1. What is Ruby on Rails? What type of applications is it used for?
2. Explain the Model-View-Controller (MVC) architecture in Rails.
3. How do you create a new Rails application?
4. What is a Rails migration? How do you create and run migrations?
5. What is ActiveRecord? How does it interact with the database?
6. What are the differences between render and redirect_to in Rails?
7. Explain the concept of routes in Rails. Where are they defined?
8. What is the Rails Asset Pipeline? Why is it useful?
9. What are Rails validations? Provide an example of using validations in a model.
10. What is the Gemfile in Rails? How do you install and manage gems?

Intermediate Questions

1. How does Rails manage database relationships? Explain belongs_to, has_many, and has_and_belongs_to_many.
2. What is RESTful routing in Rails? How do you define routes for a resource?
3. What is a helper in Rails? How are helpers different from controllers?
4. Explain the concept of partials and layouts in Rails views.
5. What is the difference between before_action, after_action, and around_action?
6. How do you perform caching in Rails? What are the different types of caching?
7. What is a Rails callback? Provide examples of before_save, after_save, and before_validation.
8. What are concerns in Rails? How are they used to organize code?
9. Explain the difference between a polymorphic association and a single-table inheritance (STI).
10. What is the purpose of the Rails routes.rb file? How do you define custom routes?

Expert Questions

1. What is the difference between eager loading and lazy loading in Rails? How can you optimize queries?
2. Explain how Rails handles security. What is CSRF protection and how does Rails implement it?
3. How do you implement background jobs in Rails? What tools or gems can be used?
4. How does Rails support API development? What is the difference between Rails API-only and full-stack applications?
5. Explain the role of ActiveJob in Rails. How would you use it with a background job processor like Sidekiq?
6. What is a service object in Rails? Why is it useful for complex business logic?
7. How do you handle N+1 query problems in Rails? Provide an example.
8. What are Rails engines? How do you create and integrate them into a Rails application?
9. Explain the differences between session, cookies, and flash in Rails.
10. How do you implement multitenancy in a Rails application? What are the challenges?

General Bonus Questions (Advanced Rails Concepts)

1. How would you profile and debug performance issues in a Rails app?
2. What are the key differences between Rails 5, Rails 6, and Rails 7?
3. How would you set up WebSockets in a Rails application? Explain with ActionCable.
4. How does Rails handle file uploads? What are the differences between ActiveStorage and third-party tools like CarrierWave / S3 Bucket?
5. Explain how Rails manages dependencies and gems with Bundler.
6. How would you scale a Rails application to handle high traffic?
7. What are the differences between using puma, unicorn, or Passenger as the Rails web server?
8. How do you write integration and unit tests in Rails?
9. How do you manage database transactions in Rails for complex workflows?
10. How do you set up and optimize ActionMailer for sending emails in a Rails application?