New Release SAA-C03 AWS Certified Associate Questions

EC2 instances in private subnets cannot access the internet unless there is a NAT gateway or a NAT instance configured.

“To enable instances in a private subnet to connect to the internet or other AWS services, you can use a NAT gateway or NAT instance.”

— NAT Gateways – Amazon VPC

In this use case:

EC2 instances are in private subnets

They need to call external APIs (internet access)

The most operationally efficient and secure method is to place a NAT Gateway in a public subnet and update the route table for private subnets to route internet-bound traffic through it.

Incorrect Options:

A: Private subnets don’t support public IPs.

C: VPC peering doesn’t help reach the public internet.

D: Interface endpoints are for private connectivity to AWS services, not external APIs.

The correct answer is C because the existing application uses NFS storage for an image cache that is a few terabytes in size , and the company wants the most cost-effective cloud alternative . Amazon EFS One Zone is a managed file storage service that supports the NFS protocol , which allows the application to continue using a familiar file-based interface with minimal architectural change. Because this is a cache , not primary durable data, storing it in a One Zone file system is a cost-optimized choice compared with a Regional EFS deployment.

Amazon EFS is designed for shared file storage and can scale to multiple terabytes automatically. It avoids the operational overhead of managing EC2 instances and local disks for cache storage. It is also better aligned than object storage for workloads that already expect direct NFS semantics. The application can mount the EFS file system and use it as the cache backend without redesigning around object APIs or in-memory caching models.

Option A is incorrect because ElastiCache Memcached is an in-memory cache and is typically much more expensive for multi-terabyte cache data than file storage. Option B is incorrect because using EC2 instance store volumes creates significant management overhead and the cache would be lost whenever instances are terminated or replaced. Option D is incorrect because Amazon S3 Express One Zone is object storage, not NFS storage, and would require application redesign and additional metadata management in DynamoDB.

AWS storage guidance recommends matching file-based workloads to managed file services. For a large NFS-based cache , Amazon EFS One Zone is the most cost-effective and operationally simple solution.

Amazon API Gateway supportsresource policies, which allow you to control access to your API by specifying the IP addresses or ranges that can access the API. By creating a resource policythat explicitly denies access to any IP address outside the allowed set, you can ensure that only trusted IP addresses (such as those from your internal network) can access the critical information in your API. This approach provides fine-grained access control without the need for additional infrastructure or complex configurations.

Option A (Private integration): API Gateway private integrations are for creating private APIs that are only accessible within a VPC, but this solution is about restricting access to certain IP addresses.

Option C (Private subnet and ACLs): Deploying the API in a private subnet and using network ACLs adds unnecessary complexity and isn ' t the best fit for HTTP APIs.

Option D (Security group): API Gateway doesn ' t have a security group because it isn ' t a resource inside a VPC. Instead, resource policies are the correct mechanism for controlling IP-based access.

AWS References:

Controlling Access to API Gateway with Resource Policies