SAA-C03 Exam Dumps - AWS Certified Solutions Architect - Associate (SAA-C03)

Amazon EFS provides a fully managed, highly available, and shared file system that can be mounted by instances across multiple Availability Zones. This ensures consistency of files between EC2 instances and avoids replication issues. EBS volumes, in contrast, are AZ-scoped and not designed for multi-instance sharing. Options A and B rely on custom replication or manual file handling, which increases operational overhead and risks inconsistencies. Option D does not solve the shared access and consistency requirement. By migrating storage to EFS, both EC2 instances will read and write to the same storage system, ensuring that users always access the latest files without 404 errors.

The key requirements are (1) MySQL compatibility for existing applications and (2) the ability to scale automatically during demand spikes for a transactional workload. Amazon Aurora (MySQL-compatible) satisfies compatibility while providing managed database capabilities designed for high performance and scalability. Using AWS Database Migration Service (DMS) is operationally efficient for migration because it supports moving data from on-premises databases to AWS with options for continuous replication to minimize downtime, which is commonly required for transactional systems.

Turning on Aurora Auto Scaling (for Aurora Replicas) allows the database tier to automatically add or remove read replicas based on demand, which helps absorb increased read traffic without manual intervention. This meets the “scale automatically” requirement more directly than simply scaling storage. (Write scaling is addressed through Aurora’s architecture and capacity planning; for many workloads, scaling reads is the dominant elasticity need.)

Option A only mentions configuring storage scaling, which does not address compute scaling during load increases; RDS storage autoscaling helps prevent running out of space but does not automatically add compute capacity in response to demand. Option B is incorrect because Amazon Redshift is a data warehouse designed for analytics/OLAP, not a transactional MySQL OLTP replacement, and mysqldump to Redshift does not preserve application compatibility. Option D changes the data model by migrating to DynamoDB, which is not MySQL-compatible and would require application redesign—violating the compatibility requirement.

Therefore, C best satisfies compatibility and automatic scaling needs while using managed services that reduce operational overhead during and after migration.

For Amazon RDS for PostgreSQL, AWS provides IAM database authentication. With this feature, applications do not use stored long-term usernames and passwords. Instead, they use temporary authentication tokens that are generated by AWS and validated by the RDS database.

The AWS best practice pattern is:

Attach an IAM role to the EC2 instances (instance profile).

Grant that role the necessary permissions (for example, rds-db:connect) to the specific RDS database user.

The application running on the EC2 instance uses the role’s temporary credentials to call the RDS token-generation API and obtain a short-lived authentication token.

The application then uses this token as the password when connecting to RDS for PostgreSQL.

This removes the need to store long-term credentials in the application or on the instance and uses IAM roles with temporary credentials, aligning with the security requirement.

Option A still relies on stored credentials (even if in Secrets Manager), which are long-lived and rotated but not token-based per-connection IAM authentication.

Option B uses static passwords and IP-based access, which does not meet the “no long-term credentials” requirement.

Option C stores long-term IAM user keys on the instances, which is explicitly against best practices and does not directly integrate with RDS authentication.

The correct answer is A because the application must accept TLS connections from IPv4 clients , provide outbound internet access , present a single entry point , and maintain the lowest possible attack surface . Placing the Amazon ECS tasks in private subnets is the key security design decision because it prevents direct inbound access from the internet to the tasks themselves. The public-facing entry point is the load balancer, while outbound internet access for the private tasks is provided through a NAT gateway in the public subnet.

A Network Load Balancer (NLB) is well suited for handling TLS at Layer 4 and can expose a single public endpoint for client connections. With awsvpc network mode, each ECS task receives its own elastic network interface, making it straightforward to place tasks securely in private subnets while still registering them as targets behind the load balancer.

Option B is incorrect because an egress-only internet gateway is for IPv6 outbound traffic only , while the requirement specifically mentions IPv4 clients . Option C is incorrect because placing ECS tasks in public subnets increases the attack surface by exposing application infrastructure more directly to the internet. Option D is also incorrect for two reasons: it uses an egress-only internet gateway , which does not satisfy IPv4 outbound needs, and it places tasks in public subnets , which violates the goal of minimizing exposure.

AWS security design guidance emphasizes reducing exposure by placing application workloads in private subnets and exposing only the required front-end endpoint. Therefore, a public NLB with private ECS tasks and a NAT gateway is the most secure and appropriate architecture.

Amazon Elastic File System (EFS) is a managed file storage service that can be mounted across multiple EC2 instances. It provides a scalable and high-performing solution to share data among instances within a VPC.

High Performance: EFS provides scalable performance for workloads that require high throughput and IOPS. It is particularly well-suited for applications that need to share data across multiple instances.

Ease of Use: EFS can be easily mounted on multiple instances across different Availability Zones, providing a shared file system accessible to all the instances within the VPC.

Security: EFS can be configured to ensure that data remains within the VPC, and it supports encryption at rest and in transit.

Why Not Other Options?:

Option A (Amazon S3 bucket with APIs): While S3 is excellent for object storage, it is not a file system and does not provide the low-latency access required for shared data between instances.

Option B (S3 bucket as a mounted volume): S3 is not designed to be mounted as a file system, and this approach would introduce unnecessary complexity and latency.

Option C (EBS volume shared across instances): EBS volumes cannot be attached to multiple instances simultaneously. It is not designed to be shared across instances like EFS.

AWS References:

Amazon EFS- Overview of Amazon EFS and its features.

Best Practices for Amazon EFS- Recommendations for using EFS with multiple instances.

Comprehensive and Detailed 250 to 300 words of Explanation (AWS documentation-based, no links):

The requirements are straightforward: expose the Lambda microservice through an HTTPS endpoint and authenticate calls using IAM. Lambda function URLs are a built-in feature that provides a dedicated HTTPS endpoint for a Lambda function without requiring API Gateway, ALB, or CloudFront. When configured with the authentication type AWS_IAM, the endpoint requires requests to be signed with AWS Signature Version 4 and authorized by IAM policies. This directly satisfies the “must use IAM to authenticate calls” requirement with the least architectural complexity.

Option A can also secure an endpoint with IAM, but it proposes using a Lambda authorizer, which is typically used for custom authorizers (JWT/OAuth/Cognito/external identity). For IAM authentication in API Gateway, you generally use IAM authorization on the method, not an authorizer function. Also, API Gateway REST APIs introduce additional service configuration and per-request costs when a simpler managed option exists that meets the requirements.

Options C and D are not appropriate. Lambda@Edge and CloudFront Functions run at CloudFront edge locations with different programming and deployment models; they are designed for CDN request/response manipulation, not as the primary mechanism to expose a regional Lambda microservice endpoint with IAM authentication. CloudFront Functions in particular is for lightweight JavaScript at the edge and does not provide a native “AWS_IAM authentication type” for invoking an origin Lambda as a microservice endpoint.

Therefore, B is the cleanest and most secure fit: a native HTTPS endpoint backed by Lambda, protected with IAM-based SigV4 authentication.

Maintaining two NAT gateways for production ensures high availability. Reducing to one NAT gateway in non-production environments lowers cost while maintaining necessary connectivity. This approach is recommended by AWS for cost optimization in non-critical environments.

Reference Extract:

" For environments that do not require high availability, you can reduce costs by using a single NAT gateway and updating route tables accordingly. "

Source: AWS Certified Solutions Architect – Official Study Guide, Cost Optimization and NAT Gateway section.

AWS DataSync provides managed, incremental, parallelized transfers between EFS file systems across Regions, supporting scheduled or continuously running tasks with automatic change detection, encryption in transit, and integrity verification. You can configure two tasks in opposite directions (bi-directional) to achieve two-way synchronization with high availability using agents in each Region and EFS locations connected via VPC endpoints. Native EFS replication (B) is one-way (read-only target) and not intended for active/active two-way sync. Options A and D rely on custom rsync and cross-Region mounts or SFTP, which introduce operational overhead, latency, and fail to provide resilient, managed synchronization. DataSync minimizes operational burden while delivering fault-tolerant, scalable, cross-Region EFS sync.