Hi there,
This is my first foray into using Freelancer, keen to offer you my services at a greatly reduced rate as an intro to what I can offer.
Having experienced the same issues for my clients, and assisted them in getting the maximum performance from their site, I can definitely assist you for this task at hand and others if required.
For database related performance issues, I can assist you in working out where the bottleneck exists (too many table joins, non optimised tables etc) and recommend to you the best course of action.
For website related performance issues, I can assist in working out the best strategy utilising both server (image sprites, consolidated scripts etc) and client side optimisation. This could include recommendations for you to provide to your server hosts to get the most out of your website.
To get started, I'd need a summary of the site needing optimisation and its basic make-up. Access (FTP/SSH) to the files and ability to connect to the database (SSH, user with sufficient privileges to view and query database) would help me get a better understanding of what's involved, and to get the maximum return from our services.
Look forward to answering your questions,
Megumi