Just need a little advice here if anyone can help. Currently i have nginx running on a virtual private server, i am looking into installing node.js so i can use AjaxIM (http://ajaxim.com/) , and installing memcached, apc, and varnish. The main page of the site will probably be updated around once an hour, and i plan on just using the default settings for each caching plugin, so I am wondering if all of these are going to work together. Also, does anyone have any experience with node.js querying a mysql database, and would i be saving myself some trouble by skipping some of these plugins and just using node.js for the sake of speed.
Leaving out APC, then yes, all these work great together, but unless you have a lot of semi-static content, you are probably not going to benefit all that much from Varnish, so you might leave that out for starters.
There is a whole host of options for accessing MySQL from Node.js. I haven’t used any of them, but db-mysql looks promising. It's part of Node.js DB – you can find some examples there.