Everything needs to be optimized for maximum performance / throughput / requests, minimal response time for a PHP/MySQL website.
- Linux Setup: Firewall, System Level (OpenFile Handlers, sysctl config)
- Apache Setup (or alternatives) and optimization
- MySQL Master-Master replication
- common directory for uploaded files (GridFS, Mount, other solutions)
- NGinx as a load balancer
- security tools like ssh black, change SSH port etc..
- setup basic monitoring and alerts via email
- no email server is required
- setup solr cloud (but I could do this also myself)
You need to know what you are doing and have experience with high-traffic websites and MySQL Master-Master setups.