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The issue described in the question, where incoming traffic seems to favor one EC2 instance, is often caused by session affinity (also known as sticky sessions) being enabled on the Application Load Balancer (ALB). When session affinity is enabled, the ALB routes requests from the same client to the same EC2 instance. This can cause an imbalance in traffic distribution, leading to performance bottlenecks on certain instances while others remain underutilized.

To resolve this issue, disabling session affinity ensures that the ALB distributes incoming traffic evenly across all EC2 instances, allowing better load distribution and reducing latency. The ALB will rely on its round-robin or least outstanding requests algorithm (depending on the configuration) to distribute traffic more evenly across instances.

Option B (Network Load Balancer): The NLB is designed for Layer 4 (TCP) traffic and low latency use cases, but it is not needed here as the problem is with load balancing logic at the application layer (Layer 7). The ALB is more appropriate for HTTP/HTTPS traffic.

Option C (Increase EC2 Instances): Adding more EC2 instances does not solve the root issue of uneven traffic distribution.

Option D (Health Check Frequency): Adjusting health check frequency won't address the imbalance caused by session affinity.

AWS References:

Application Load Balancer Sticky Sessions

When operating in disconnected or limited-connectivity environments, such as ships at sea, AWS recommends using AWS Snowball Edge devices to host local compute and storage workloads. Snowball Edge supports Amazon EC2 instances and AWS IoT Greengrass, and can run Amazon EKS Anywhere for local Kubernetes cluster deployments.

From AWS Documentation:

“You can use AWS Snowball Edge devices to run compute-intensive applications in remote or disconnected locations. Snowball Edge devices support running Amazon EC2 instances and Amazon EKS Anywhere clusters.”

(Source: AWS Snow Family – Developer Guide)

Why A is correct:

Snowball Edge provides local compute and storage even without internet connectivity.

Multiple Snowball Edge devices can be clustered together for high availability and failover.

Fully self-contained environment suitable for ships or field operations.

Why the others are incorrect:

B, C, D require network connectivity to AWS Regions or Zones (Local Zone, Outposts, Wavelength), which is not available at sea. These options cannot operate fully disconnected.

Using S3 gateway endpoints allows private and cost-free access to S3 without routing traffic through a NAT gateway. NAT gateway traffic incurs charges, especially when used across multiple Availability Zones.

By using an S3 gateway endpoint, EC2 instances in private subnets can access S3 directly without needing internet access, reducing both data transfer and NAT gateway costs.

Interface endpoints are more expensive and typically used for services like API Gateway or Systems Manager.

For processing thousands of images and generating large files while minimizing manual tasks and operational overhead, usingAWS Batchis the best solution. AWS Batch allows you to run large-scale, parallel, and managed batch computing jobs without needing to manage the underlying infrastructure.

AWS Batch: Automates the image processing jobs, dynamically allocating the necessary resources based on the job requirements, which reduces operational overhead.

AWS Step Functions: Orchestrates the entire image processing workflow, ensuring that tasks are executed in the correct sequence, improving manageability.

Amazon S3: Stores the processed files, providing scalable and cost-effective storage.

Option A (ECS with EC2 Spot Instances): While cost-effective, managing ECS and Spot Instances involves more operational effort.

Option C (Lambda with EC2 Spot): Lambda functions have size and duration limitations, making them less suited for large image processing tasks.

Option D (EC2 with Step Functions): Managing EC2 instances involves more overhead than using AWS Batch.

AWS References:

AWS Batch

AWS Step Functions