Here's the thing about performance: even "well written" code can be unperformant. It could be a query that isn't optimised with an index in the db, it could be

Here's the thing about performance: even "well written" code can be unperformant. It could be a query that isn't optimised with an index in the db, it could be best practice code that doesn't work well in the context of your app, any number of things. At my last job we had a page that looked to be very well written, but it was taking 30+ seconds to render the page. Turns out to be a method we were calling 10x too many, because someone had benchmarked it in isolation and it didn't have any performance impact. However in conjunction with some of the data that occasionally passed through that method, those 10x calls ended up being a couple of seconds each. That's an extreme example but there's little things you can do everywhere on a rails app if you know what you're looking for, and I would expect this to be the case in any web framework.