What SOA-C03 Questions and Answers feature?

Layer 7 (application-layer) HTTP status codes such as 200, 404, and 500 are generated by web-facing services that process HTTP requests. In this architecture, both CloudFront and the Application Load Balancer (ALB) operate at Layer 7 and record HTTP response information in their access logs.

ALB access logs include detailed request and response data such as client IP address, request path, target response status code, and latency. These logs are essential for analyzing how backend EC2 instances respond to client requests.

CloudFront access logs record viewer requests and responses at the edge locations. These logs also include HTTP status codes returned to the client, making them critical for understanding end-user experience and edge-level behavior.

VPC Flow Logs capture network-level (Layer 3 and 4) traffic metadata such as source IP, destination IP, ports, and protocol. They do not contain HTTP status codes. AWS CloudTrail logs API calls to AWS services and does not capture application response codes. RDS logs contain database-related information, not HTTP responses.

Therefore, the correct sources for HTTP Layer 7 status codes are ALB access logs and CloudFront access logs.

Comprehensive and Detailed Explanation From Exact Extract of AWS CloudOps Documents:

The requirement is classic active-passive (production in us-east-1, DR in us-west-2 “only for failover”). The most operationally efficient and purpose-built solution is Route 53 failover routing combined with health checks. With failover routing, Route 53 designates one record as PRIMARY (us-east-1) and another as SECONDARY (us-west-2). Route 53 continuously evaluates the health check associated with the primary endpoint (commonly the ALB DNS name or a specific health-check path). If the primary fails, Route 53 automatically returns the secondary record, directing client DNS resolution to the DR region. This ensures us-west-2 is used only when us-east-1 is unhealthy, directly matching the requirement.

Latency routing (Option B) is designed to route users to the region with the lowest latency, which can actively send traffic to us-west-2 even when us-east-1 is healthy—violating the “DR only” constraint. Options C and D introduce custom automation (CloudWatch + Lambda + DNS record updates) that increases operational overhead, adds failure modes, and is unnecessary because Route 53 already provides managed health-check-based failover. Additionally, “EC2 instance terminated” is not a reliable proxy for full application availability, and DNS modification automation is more complex than using native Route 53 failover policies.

The Storage Gateway service enables hybrid cloud backup by presenting local block storage that synchronizes with AWS cloud storage. For scenarios where all data must remain available locally while still backed up to AWS, the correct mode is gateway-stored volumes.

AWS documentation defines:

“Use stored volumes if you want to keep all your data locally while asynchronously backing up point-in-time snapshots to Amazon S3 for durable storage.”

These volumes expose an iSCSI interface compatible with POSIX file systems, allowing direct use by on-premises backup software.

Gateway-cached volumes (Option C) store primary data in AWS with limited local cache, violating the “all data must be available locally” requirement. Options A and B are object-based storage solutions, not compatible with POSIX or block-based backup applications.

Therefore, Option D fully satisfies CloudOps reliability and continuity best practices by ensuring local availability, cloud durability, and POSIX compatibility for backups.