It’s often much more efficient to access DOM properties directly, rather than using jQuery. The downside to that approach is that there are differences between the various browsers, so in some cases it introduces bigger problems than the extra performance overhead.
TJ Stein gave a really good presentation at WordCamp Chicago 2011 about scaling and performance issues with WordPress installations. He focuses a lot on using ngnix instead of Apache, but also covers PHP object caching, Varnish, CDNs, benchmarking, etc. It’s a good overview of current practices, but there’s also a lot of specific tips throughout.
Mark Maunder benchmarked several performance tuning measures with a WordPress installation on a VPS server to show which are most effective. The biggest improvements were from installing PHP-APC, setting up Nginx to proxy concurrent connections for Apache, and using MySQL’s query cache.
Apache’s default settings assume it’s running under a dedicated box with at least 2GB of RAM, so they don’t perform very well in a VPS that may only have 500MB. I recently made some tweaks to several VPS’s that reduced memory usage by 300-400MB without degrading performance. Apache Performance Tuning is a good article that […]
Ian Gilfillan’s article on using indexes in MySQL has a good explanation of how to use the EXPLAIN statement to analyze a query, and what to look out for. You can also check out Jesse Farmer’s optimization tips for a primer on more advanced techniques.