Which solution will meet these requirements MOST cost-effectively?

Explanations:

An Application Load Balancer (ALB) operates at the application layer (Layer 7) and is designed primarily for HTTP/HTTPS traffic. It does not support UDP traffic, which is essential for the low-latency requirements of online gaming. Therefore, it is not suitable for handling millions of UDP requests efficiently.

A Gateway Load Balancer is designed for deploying, scaling, and managing third-party virtual appliances, such as firewalls and intrusion detection systems. It operates at Layer 3 and is not optimized for direct handling of high-volume UDP traffic for game servers. While it can work with TCP and UDP, it is not the best fit for ultra-low latency gaming applications compared to a Network Load Balancer.

A Network Load Balancer (NLB) operates at Layer 4 and is designed to handle millions of requests per second while maintaining ultra-low latency. It supports both TCP and UDP protocols, making it ideal for gaming applications that require fast, efficient traffic handling. By using an NLB, the company can ensure that UDP traffic is routed directly to the EC2 instances, maximizing performance and cost-effectiveness.

Launching identical sets of game servers in separate AWS Regions introduces complexity and potential latency issues due to the geographic distance between regions. This solution is not cost-effective and may lead to increased operational overhead and inconsistency in user experience, especially since it doesn’t directly address the ultra-low latency requirement for UDP traffic.