Basically if one of your controller has more than 10 lines of processing and you don't need to present the data to the user immediately, you can put that into a

Basically if one of your controller has more than 10 lines of processing and you don't need to present the data to the user immediately, you can put that into a job, for example when a user register, you can add the new record to the database and redirect him, but you can send the welcome email 1-2 minutes late. And for presenting data, yeah, go cache everything, also take a look inside rails partial cache features, for example in a page, even that the results are dynamically generated, you can cache things like categories for example, or the blog post, and retrieve just the comments.