A list of some baseline Rails interview questions
Latest commit c98f234 Mar 28, 2016 @afeld fix broken links
Failed to load latest commit information.
README.md fix broken links Mar 28, 2016


Rails Interview Questions

I get a fair number of questions via Hacker Hours and elsewhere regarding what questions to use/expect in an interview for a Rails developer, so figured I would get it together in a tidy list. Pull requests welcome.



  • Personalize your list of questions.
  • Don't ask questions you don't know the answers to.
  • Mix trivia questions with open-ended ones.
  • Use Codr or a similar online collaborative text editor for doing coding challenges
    • Can be seen in real-time by remote team members
    • The unique URL with the solution can be easily sent around or added wherever you a tracking information about the candidate


  • Don't study to the test. Not all of these questions will be used, and others will be asked that aren't covered here. Know your stuff.
  • Rails skills != CS skills
  • Know whether you are interviewing for a full-stack vs. backend-focused position.
  • Have code up on Github/Bitbucket/wherever - the more side projects you have to talk about, the better.
  • Be comfortable with some version control system.
  • Community awareness and resourcefulness can be as important as technical knowledge.

The Questions


  • What is a tree? What is a DAG?
  • Pseudo-code depth-first and breadth-first search.
  • Given a sorted array, what is the fastest way to find a element? What is the Big-O time to do so?
  • Explain how ajax works, hitting all parts of the stack. (@abestanway)


  • What is the difference between a lambda, a block and a proc? [I have gotten this one at every Ruby interview I've been in]
  • How do you sort an Array of objects by a particular attribute? What is a better way to do sorting with ActiveRecord?
  • What are some of your favorite gems? What are their alternatives?
  • In Ruby, which is generally the better option: a recursive function or an iterative one?
  • What are #method_missing and #send? Why are they useful?
  • What are the various Ruby runtimes, and how are they different?
  • Define "Matz".


  • What is the general history of Rails?
  • What is new in Rails 4?
  • Explain the different pieces of Rails.
  • Walk through the flow of a request through Rails.
  • What are the different server options for running a Rails/Rack app?
  • Explain CSRF and how Rails combats it.
  • Explain mass-assignment vulnerability.
  • Define "DHH".
  • Define "tenderlove".
  • Why do some people say "Rails can't scale"?
  • What is Rack?
  • What is middleware? How does it compare to controller filters/actions?
  • Explain various forms of caching available in Rails.
  • What are some Ruby web server options?
  • How is something like 30.seconds.ago implemented? (c/o @harrisj)
  • On a scale of @gorbypuff (0) to @tenderlove (10), how would you rate your Rails proficiency?


(no particular order)

Creative Commons License
Rails Interview Questions by Aidan Feldman is licensed under a Creative Commons Attribution 3.0 Unported License.