In load balancing, a backend pool is a group of resources, such as Droplets, whose traffic are managed by the load balancer.
The Droplets in a load balancer’s backend pool must be in the same region as the load balancer. All DigitalOcean Load Balancers automatically monitor their backend pools and only send requests to Droplets that pass health checks.
Setting up a load balancer is a two-step process: creating the load balancer and then choosing Droplets for its backend pool. For more information about creating load balancers, see How to Create Load Balancers.