Load balancing

A load balancer spreads incoming traffic across healthy targets and takes unhealthy ones out of rotation. On AWS, the decision is less whether to use one than which type. The types work at different network layers and route on different information.

Start with Elastic Load Balancing. It compares the load balancer types by layer, protocols, routing capability, target types and cross-zone behaviour, and gives a way to choose between them.

Gateway Load Balancer serves a different purpose. It does not spread application traffic. Instead, it inserts third-party firewalls and inspection appliances into a traffic path without the applications on either side needing to know they are there.