Performance improvement of a website

We have a website selling a huge number of products (around 100 000 products). A custom module has been developed where we research some associated products based on some criterias. We are looking for someone with a very good knowledge of the Magento structure, and a proven experience in optimizing Magento for large number of products. Please contact me with your references. I will provide you then the link to the module which needs to be optimized.