Before we talk performance, lets talk entropy. Entropy usually refers to the idea that everything in the universe eventually moves from order to disorder, and entropy is the measurement of that change.
Like entropy, the performance of a Rails app will trend toward disorder. An N+1 database query here, a forgotten pagination implementation there, a missing index here, etc. This performance debt builds over time, and suddenly...we've got a slow app.
Where do you start knocking down this performance debt? Surely, not everything is slow, right? Let's perform a Rails performance audit.
In 10 minutes or less, you'll have a good idea of where your app stands and where to focus your efforts by following this 5-point performance audit. At each step of the audit, I'll work through the analysis on a real production app so you can see an audit applied.