The WSO2 Elastic Load Balancer is built using Apache Tribes, which is the group management framework used by Apache Tomcat as well as Apache Axis2, Apache Axis2 clustering module, Apache Synapse - one of the best performant mediation frameworks, and the autoscaling component from the award-winning WSO2 Carbon framework. The diagram below depicts its high-level architectural view.
Figure: The WSO2 ELB Architectural Components
WSO2 Carbon Auto-Scaling Component
Keeps track of the traffic to each Cloud Service cluster, and makes decisions related to scaling the system up and down depending on the load fluctuation. It is also responsible for keeping a sanity check on the system. This sanity check ensures that the minimum system configuration, such as the minimum number of running instances of each Service and load balancer cluster is maintained at all times.