by Irakli Nadareishvili, Director of Product Development at Phase2, @inadarei on Twitter.
Erik Summerfield, Software Developer at Phase2
You will probably have a number of contrib modules, and the queries that these modules execute can have a huge impact on the performance of your site.
Performance on the web is usually described by speed and scalability.
Speed is measured in seconds, and tells you how long it takes a single user to load a single page and all the assets that make up that page.