Consulting on Architecture for Multi-server Joomla/MySQL Website

We have a mature Joomla website with thousands of pages and 70,000+ active users. The site has 1 MySQL database server with 2-4 CentOS/NGINX servers and a load balancer. The load on these servers is higher than it should be and the site has stability issues frequently. We're looking for an expert(s) in high end CMS/Joomla websites to review our NGINX settings, MySQl setup (add High Availability and or migrate to a more scalable database) and setup with CENTOS and Rsync. We have one main server our bloggers and content contributors publish to that replicates to the other web servers. We use a cloud platform to replicate and backup servers. We use Rack space for file storage of images, power points and videos and we are open to switching this to a different CDN. We offer religious and family teaching resources. If you have expertise with fault tolerant web applications like described above we are looking for you. We're looking for a consultant that can either design or enhance our existing architecture and if you can assist with the technical work to make the needed changes even better.