Recommendable is a gem that allows you to quickly add a recommendation engine for Likes and Dislikes to your Ruby application using my version of Jaccardian similarity and memory-based collaborative filtering. Bundling one of the queueing systems above is highly recommended to avoid having to manually refresh users' recommendations. If you bundle Sidekiq, you should also include 'sidekiq-middleware' in your Gemfile to ensure that a user will not get enqueued more than once at a time. If bundling Resque, you should include 'resque-loner' for this. As far as I know, there is no current way to avoid duplicate jobs in DelayedJob. Queueing for Torquebox is also supported.