Which solution is the MOST cost-effective at scale?

Explanations:

Although Multi-AZ and Auto Scaling are beneficial for EC2 instances, using Elastic Block Store (EBS) volumes for large datasets such as 16 TB is not the most cost-effective solution. EBS volumes are costly at scale and don’t offer automatic scalability. The solution doesn’t address the need for a more scalable database solution.

While Amazon ECS and Aurora MySQL are scalable solutions, designing a Docker-based containerized application adds unnecessary complexity to the current environment. The focus should be on database scalability and cost-efficiency, rather than containerizing the application. Aurora MySQL is a better choice than EC2-hosted MySQL for scalability, but the application containerization isn’t necessary.

Migrating to Aurora MySQL Multi-AZ is the best option for high availability, scalability, and performance. Aurora offers automated storage scaling, unlike EBS volumes. This reduces operational overhead and is more cost-effective at scale. The use of EC2 Auto Scaling and Elastic Load Balancing ensures application scalability and availability.

This option is similar to C but introduces unnecessary complexity with storage checks and Lambda functions to grow Aurora MySQL storage. Aurora MySQL automatically scales storage, so this manual intervention is unnecessary. Additionally, the focus on reserved instances for EC2 increases costs, whereas using on-demand scaling with Auto Scaling is more flexible and cost-efficient.