MySQL Security and Optimization

We are looking for a Web security expert that can re-code for Full proof from hacking. Need to have 3 tier MVC architecture and MySQL optimization for handling large database. We have a high traffic website with a large database (800Mb). I will give the rest of the details to the person that wins the job. Also I will have a 3rd party test your work before making the last payment. I will pay the amount of bid only after the tasks have been completed and working fully. I will hold the payment for 45 days until this has been confirmed. No partial payments - sorry! When conditions have been met successfully, you will be paid in full. The bidder must show us some of their previous work such as websites/blogs that you have created. Only experience bidders with a proven record will be considered. If I am satisfied with your work, you will definitely be awarded future projects from us.