Scaled-out Architectures

Web Servers: Apache HTTPD & NGINX
Load Balancers: HAProxy & NGINX
HTTP Accelerator: Varnish
In-memory Object Cache: Memcached & Redis
Database: MySQL Replication & Galera Cluster
Search: Apache Solr & Elastisearch
Message Queues: RabbitMQ & ActiveMQ
Java Application Server: JBoss & Tomcat
Messaging Servers: Postfix & Horde
Directory Server: OpenLDAP & FreeIPA
Linux Cluster: Corosync & Pacemaker
Virtualization: KVM/libvirt, RHEV & Oracle VM

AWS & OpenStack

Multi-AZ & Multi-Region Architectures
AWS CloudFormation
AWS OpsWorks
AWS Auto Scaling
OpenStack IaaS Private Cloud Architecture
Automation: Puppet & Ansible

Hadoop, NoSQL & MySQL

Hadoop HDFS & MapReduce
Hadoop Pig, Hive & Mahout
Hadoop Hbase
Apache ZooKeeper
Apache Cassandra
MongoDB
CouchBase
MySQL/MariaDB Replication
MySQL/MariaDB Galera Cluster
ELK (Elasticsearch/LogStash/Kibana) & Graylog