What are the best practices for scaling a Ruby on Rails application?

The Ruby on Rails application should be optimized for scaling by taking on more users than usual for performance. Keeping pace with the best practices, lighten the load off the database by caching strategies, including fragment caching and Redis. Enhancement of load balancing across multiple servers should also be done, including background job processing handled by tools like Sidekiq, which handle responsiveness. That performance remains optimized on scaling of the application, regarding database queries and indexing, while making use of content delivery networks for assets.