Nice thread, I'm a bit of a caching geek so let me point you to a few things:
Firstly... take a look at the cache cannon hack I was making for VB 2.x, it was abandoned as I was making it for a very specific person who was on a safe_mode protected box and it wouldn't work with safe_mode... however it did work fine on a normal box.
Anyhow, link for that:
https://vborg.vbsupport.ru/showthread.php?t=36000
That created 100% flat filed and browsable forums, threads and posts.
For searchability you would have to consider something that indexed the threads seperately (such as a site indexing tool) or simply embed a Google search box
Secondly, if you want to improve caching for existing items but leave them in the database, consider using one of the PEAR cache libraries:
http://pear.php.net/packages.php?cat...atname=Caching
Thirdly... and possibly the most interesting... dump your posts, threads and forums data to XML files, embed at the top of these the path of an applicable XSLT file to render them, and offer an XPATH way to search, sort and browse them.
That is technically possible and feasible, though it will depend on your skills with XML, XSLT and XPATH as to whether you can make that work. I tell you one thing though... it would be a hell of a thing to see and would allow you to change the presentation of it over time in a way that static HTML would not.
The XSLT transformation gets shifted onto the browser btw... server side transformation would be intensive to say the least.
Helpful starters there:
A SQL 2 XML package:
http://pear.php.net/package/XML_sql2xml
XML Transformer package:
http://pear.php.net/package/XML_Transformer
XML XPath Queries package:
http://pear.php.net/package/XML_XPath