I spend most of my working life building website code at work, and sometimes I get involved in performance work with that sort of system. In fact I've written and presented on that topic for Sitecore in the past. But some code I've been working on in my own time needs much more focus on code performance than that - the maths-heavy code for ray tracing. I've been looking at some optimisiations for that recently. And one thing that this has reinforced for me is how "easy to write" code can have some performance challenges...
I got the chance to speak at the Manchester Sitecore user group recently, introducing some tools and tricks that can be used to measure site performance while you're developing your Sitecore code. For anyone who wasn't there (and those who were but, want to refer back to what I said) here's a summary of the important bits of content from that talk...