Amazon Web Services Updated SAA-C03 Exam Questions and Answers by philip

Instances in a private subnet cannot directly reach the internet because they do not have public IP addresses and the private subnet route table typically does not send 0.0.0.0/0 traffic to an internet gateway. However, these instances still need outbound-only internet access to download patches and updates while remaining inaccessible from the internet. The standard AWS design to achieve this is a NAT gateway deployed in a public subnet.

Option C is required because a NAT gateway must reside in a public subnet that has a route to the internet gateway. This allows the NAT gateway to forward outbound traffic from private instances to the internet and return responses, without allowing inbound connections initiated from the internet to those instances.

Option A is required because a NAT gateway uses an Elastic IP address to represent its public-facing identity on the internet. Without an Elastic IP, the NAT gateway cannot communicate with internet endpoints. The Elastic IP is associated with the NAT gateway, not with the internet gateway.

Option B is required because the private subnet needs a route for 0.0.0.0/0 (default route) that targets the NAT gateway. This ensures that outbound internet-bound traffic from the private instances is sent to the NAT gateway rather than being dropped.

Option D is incorrect because a NAT gateway in a private subnet would not have a working route to the internet gateway and would not provide internet egress. Option E is incorrect because the public subnet’s default route should point to the internet gateway, not to the NAT gateway. Option F is incorrect because you do not associate Elastic IPs with an internet gateway.

Therefore, A, B, and C correctly implement private subnet outbound internet access while keeping the instances unreachable from the internet.

Amazon S3 Intelligent-Tiering is designed for data with unknown or changing access patterns. It automatically moves data between frequent and infrequent access tiers based on usage. This tier offers immediate access to all objects, regardless of which tier they are stored in, while optimizing storage costs. S3 Intelligent-Tiering also provides the same high durability, availability, and security as other S3 storage classes and supports access from external resources using standard S3 APIs. Lifecycle policies and Glacier classes are more suitable for archival when infrequent access is predictable, but retrieval from Glacier classes is not immediate and incurs extra charges and delays.

Reference Extract from AWS Documentation / Study Guide:

" S3 Intelligent-Tiering is designed to optimize costs by automatically moving data between two access tiers when access patterns change. Data is always available and immediately accessible, making it ideal for unknown or unpredictable access patterns. "

Source: AWS Certified Solutions Architect – Official Study Guide, S3 Storage Classes section.

To enable DNS resolution from AWS VPCs to on-premises DNS servers over Direct Connect or VPN, AWS recommends using Amazon Route 53 Resolver with outbound endpoints. An outbound endpoint allows DNS queries originating in the VPC to be forwarded to a customer-managed DNS server (e.g., on-prem).

Next, a forwarding rule (Forward type) must be created to forward DNS queries for the custom domain internal.example.com to the on-premises DNS IP addresses. This rule defines what domain names are forwarded and to which DNS servers.

Finally, the rule must be associated with all workload VPCs to allow those VPCs to use the rule. There is no need to deploy endpoints in every VPC — one outbound endpoint is sufficient and can be shared across VPCs via rule association.

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Route 53 Resolver Endpoints

Best practices for hybrid DNS resolution