MySQL expert needed ASAP

We need a MySQL expert to help troubleshooting our DB problem. When the site gets busy, MySQL is very slow and site is almost unreachable. We have 2 servers: - HTTP server: Debian 6, i7-3930K hexacore, 64 GB RAM, Nginx + PHP-FPM + APC - DB server: Debian 6, i7 CPU Quadcore, 8GB RAM, MySQL Site is live and quite busy (up to 80 HTTP req/s). We will give you : - SSH root access to both servers : you will need to provide us with your RSA public key (passwords are not allowed) - user access to PHPmyadmin. We also have munin-node graphs available.