Deep vs Shallow Trees

3.1.  Programming Practices Data Structuring can influence the performance. If the logic for home page news articles is to present the latest three, the logic of looking for articles structured as /year/month/day/article is faster than sorting a large number of articles stored directly under /news.

3.3.  Convert Underperforming XSL Renderings to .NET Certain operations can be completed much more efficiently in .NET than in XSL. Use Sitecore’s browser-based debugger to identify poorly performing code for migration to pure .NET. Invoking XSL may be more expensive in .NET than executing native .NET code.  If possible, certain XSL renderings, especially those which consume a great deal of resources or can only be cached under limited conditions should be converted to .NET method renderings, sublayouts or web controls.  Expensive XSL code can be converted to .NET extension controls and functions.

The flexibility of Sitecore Query does come with a price.