Elastic Load Balancer (ELB):

• Load balancing (as a concept) is a common method used for distributing incoming traffic among servers.

• An Elastic Load Balancer is an EC2 service that automates the process of distributing incoming traffic (evenly) to all the instances that are associated with the ELB.

• An elastic load balancer can load balance traffic to multiple EC2 instances located across multiple Availability Zones.

  • This allows for highly availability and fault tolerant architecture.

• Elastic load balancing should be paired with Auto Scaling to enhance high availability and fault tolerance, AND allow for automated scalability and elasticity.

• An ELB has it's own DNS record set that allows for direct access from the open internet access.

Other important ELB facts:

• When used within a VPC, and ELB can act as an internal load balancer and load balance to internal EC2 instances on private subnets (as often done with multi-tier applications).

• ELBs will automatically stop serving traffic to an instance that becomes unhealthy (via health check).

• An ELB can help reduce compute power on an EC2 instance by allowing for an SSL certificate to be applied directly to the elastic load balancer.