Amazon SOA-C03 Exam Dumps

High availability for an EC2-based web application behind an ALB is primarily achieved by eliminating single points of failure at the infrastructure layer. A single Availability Zone (AZ) deployment is vulnerable to AZ-level impairment (power/network issues, facility events, or service disruptions). The most direct and standard AWS approach is to distribute the Auto Scaling group across multiple AZs within the same Region.

Updating the Auto Scaling group to use subnets in at least two AZs allows instances to be launched across AZs automatically. The ALB is built to route traffic across targets in multiple AZs, and Auto Scaling can replace unhealthy instances in any enabled AZ. This provides resilience without the complexity of multi-Region architectures.

Options A and B address capacity for peak load but do not address the core availability requirement. Even with more instances, a full AZ outage would still take the entire application down if all instances are in the same AZ.

Option D (multi-Region) can improve resilience further, but it introduces significantly more operational overhead: cross-Region traffic routing, data replication, DNS failover strategy, application state handling, and potentially active-active or active-passive designs. For ''make the application highly available'' from a single-AZ baseline, multi-AZ in the same Region is the standard, least-overhead improvement.

An Application Load Balancer (ALB) operates at Layer 7 (HTTP/HTTPS) and supports advanced routing features, including HTTP-to-HTTPS redirection. To meet the requirement of protecting traffic with ACM certificates and automatically redirecting HTTP requests, the ALB must be configured with two listeners.

The correct design is to create an HTTP listener on port 80 and an HTTPS listener on port 443. The SSL/TLS certificate from AWS Certificate Manager is attached to the HTTPS listener. A listener rule on port 80 redirects incoming HTTP requests to HTTPS on port 443, ensuring all client connections are encrypted.

Option A is invalid because HTTPS cannot operate on port 80. Option C uses TCP listeners, which do not support HTTP-level redirects. Option D uses a Network Load Balancer, which operates at Layer 4 and does not support HTTP redirects.

Therefore, Option B is the only solution that satisfies all requirements using AWS-native features with minimal complexity.

The PrivateDnsName attribute of an EC2 instance is automatically assigned by AWS at launch time and is a read-only property. CloudFormation does not allow users to specify this value manually.

Including PrivateDnsName in the EC2 instance properties causes validation to fail during stack creation. Outputs and Parameters sections are optional, and the VPC is implicitly defined through the subnet ID.

Therefore, attempting to set PrivateDnsName results in stack creation failure.

Route 53 alias records are designed to map custom domain names to AWS resources such as ALBs, CloudFront distributions, and S3 website endpoints. Alias records behave like A records but point to AWS-managed resources instead of IP addresses.

Alias records are preferred over CNAME records because they can be used at the zone apex (example.com), do not incur additional DNS query charges, and automatically track changes to the underlying AWS resource.

A and AAAA records require fixed IP addresses, which ALBs do not provide. CNAME records cannot be used at the root domain.

Therefore, an alias record is the correct solution.

AWS Organizations Tag Policies provide a centralized, scalable governance mechanism to standardize tagging across accounts. Tag policies let an organization define tag keys, allowed values, and tagging expectations, helping teams apply consistent tagging conventions across many accounts without building custom logic. This matches the requirement for consistent tags ''across multiple accounts'' with minimal operational overhead, because the policy is managed centrally and applied at the organization/OUs level.

For cost tracking, user-defined tags must be activated as cost allocation tags in AWS Billing and Cost Management. Enabling cost allocation tags is the required step to make those tags usable in billing views (for example, Cost Explorer allocation and reporting). Combining Tag Policies (governance/consistency) with cost allocation tag activation (billing attribution) directly meets both parts of the requirement.

Option B (CloudTrail + Lambda auto-tagging) is higher operational overhead: it requires event processing, permissions, continuous maintenance, exception handling, and careful logic to avoid incorrect tag assignments. Option C is partially relevant for compliance detection, but AWS Budgets does not ''apply tags'' to resources; Budgets is for cost/usage alerts and budget tracking. Option D can enforce tagged provisioning paths, but it's not comprehensive for all resource creation mechanisms and Trusted Advisor is not a global ''tag enforcement'' engine.

Therefore, A is the most native and least-ops approach for consistent tags across an organization and enabling cost allocation tracking.