To decouple distributed workloads and improve scalability and resiliency, Amazon SQS should be used as a reliable job queue. The compute nodes (workers) can poll the SQS queue for tasks, and EC2 Auto Scaling can dynamically scale instances based on the ApproximateNumberOfMessages metric.

From AWS Documentation:

“Amazon SQS enables you to decouple application components, allowing each part to scale independently. You can scale EC2 instances automatically based on the number of messages in the queue.”

(Source: Amazon SQS Developer Guide – Scaling Consumers with Auto Scaling)

Why B is correct:

Eliminates the single point of failure (the primary coordinator).

Enables event-driven scaling based on queue depth.

Provides durability and resiliency since messages are stored redundantly.

Fully managed and integrates seamlessly with Auto Scaling policies.

Why other options are incorrect:

A: Scheduled scaling does not respond to variable workloads.

C & D: Misuse of CloudTrail/EventBridge; not intended for workload coordination.