A company is designing a new web service that will run on Amazon EC2 instances...

A Network Load Balancer can be assigned one Elastic IP address for each Availability Zone it uses1. This allows the clients to reach the load balancer using a static IP address that can be authorized on their firewalls. An Application Load Balancer cannot be assigned an Elastic IP address2. An A record in an Amazon Route 53 hosted zone pointing to an Elastic IP address would not work because the load balancer would still use its own IP address as the source of the forwarded requests to the web service. An EC2 instance with a public IP address running as a proxy in front of the load balancer would add unnecessary complexity and cost, and would not provide the same scalability and availability as a Network Load Balancer. References: 1: Network Load Balancers - Elastic Load Balancing3, IP address type section2: How to assign Elastic IP to Application Load Balancer in AWS?4, answer section.