What should the solutions architect do to ensure that the website can scale with increasing traffic?

Explanations:

Auto scaling on the ALB does not increase the capacity of the ALB itself, and it does not impact the scaling of the containers in ECS. ALB scales automatically to handle traffic.

Aurora Auto Scaling will dynamically adjust the number of Aurora Replicas in the Aurora cluster, allowing the database to handle increased read traffic as needed.

Cross-zone load balancing on ALB distributes traffic across containers in multiple zones but does not increase the scaling capacity of the application itself.

Creating multiple ECS clusters in each Availability Zone is redundant and not required for scaling, as ECS supports multi-AZ deployments within a single cluster.

ECS Service Auto Scaling with a target tracking policy based on CPU utilization ensures that the number of Fargate tasks adjusts dynamically to handle increased traffic to the application.