Hello
I have two years experience in hosting company:
1. Configuration nginx as proxy and LB.
2. Configuration Apach for high load websites
3. Creating clusters which consist of nginx (proxy), php, static nodes and Tomcat for Java.
4. Mysql replication - Master-slave, Master-Master.
5. MariaDB and Galera clusters.
6. Configuratin Varnish and Ha proxy.
7. Monitoring of all these systems.