Ruby on Rails is a productivity-focused web framework built on strong conventions, and its interviews test MVC, ActiveRecord (its ORM), and the "convention over configuration" philosophy that makes Rails fast to build with. Here are the Ruby on Rails interview questions that actually get asked. (See also our backend guide.)
Rails fundamentals
- What is convention over configuration, and DRY?
- Explain the MVC architecture in Rails.
- The Rails request cycle — router → controller → view.
- What are migrations, and why use them?
- RESTful routes and resources.
ActiveRecord (the ORM)
- What is ActiveRecord and the active record pattern?
- Associations — has_many, belongs_to, has_many :through.
- The N+1 query problem and how
includessolves it. - Validations and callbacks.
- Scopes vs class methods.
Ruby & practical concerns
- Ruby basics — blocks, procs, lambdas, symbols vs strings.
- What are mixins and modules?
- Strong parameters; how Rails handles security (CSRF).
- Background jobs (Sidekiq) and caching.
includes is the signal of someone who's shipped real Rails, not just scaffolded a tutorial app.How to prepare
Rails rounds probe MVC, ActiveRecord, and conventions verbally. Practise explaining associations and the N+1 fix out loud. Greenroom runs spoken technical interviews that follow up on your reasoning. Pair it with our backend and SQL guides.
Frequently asked questions
What are the most common Ruby on Rails interview questions?
Common Rails questions cover convention over configuration and DRY, the MVC architecture, the request cycle, migrations, RESTful routes, ActiveRecord (the active record pattern, associations, the N+1 problem and includes, validations, callbacks, scopes), Ruby fundamentals (blocks, procs, lambdas, symbols, mixins and modules), strong parameters, CSRF protection, background jobs and caching.
What is convention over configuration in Rails?
Convention over configuration means Rails assumes sensible defaults so developers write less configuration code. If you follow Rails naming and structure conventions — like a User model mapping to a users table — the framework wires things together automatically. This dramatically speeds up development, but it means understanding the conventions is essential, since deviating from them requires explicit configuration.
What is the N+1 query problem in Rails?
The N+1 problem happens when you load a collection (1 query) and then access an associated record for each item in a loop, triggering N additional queries. In Rails you fix it with eager loading using includes, which loads the associated records in a couple of queries instead of N. Recognizing and fixing N+1 with includes is a frequent Rails interview topic.
How should I prepare for a Ruby on Rails interview?
Embrace the conventions and focus on MVC, the request cycle, and especially ActiveRecord — associations, validations, and fixing the N+1 problem with includes — plus Ruby fundamentals like blocks and modules. Practise explaining associations and the N+1 fix out loud with a voice-based mock interview that follows up, since Rails rounds probe real shipping experience.