SAA-C03 Design Resilient Architectures Practice Test 2 — 15 Questions

Question 1

A retail platform needs disaster recovery across AWS Regions. The business requirement is: RTO up to 6 hours, RPO up to 1 hour, and they want the ability to start serving quickly during a Region outage but do not want to run full production capacity continuously. Which DR strategy best fits these requirements?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Warm standby, keeping a reduced but ready-to-scale environment in the secondary Region.. Warm standby is the best fit because it maintains a scaled-down but fully functional copy of the production environment in the secondary Region, allowing the RTO of 6 hours and RPO of 1 hour to be met without running full production capacity continuously. During a disaster, the standby environment can be scaled up quickly to serve traffic, balancing cost and recovery speed.

Answer

Backup and restore only, with no continuously running infrastructure in the secondary Region.

Answer

Pilot light, keeping only the minimum resources needed to bootstrap the environment.

Answer

Multi-site active-active, serving production traffic from both Regions at all times.

Question 2

Your order-processing system uses EventBridge rules to send events to a Lambda function that updates order status. Over the last week, some events fail with a transient database timeout, and the Lambda retries intermittently but then the events are lost (no alerts after failures). You want at-least-once processing, bounded retries, and a way to inspect unprocessable events for later reprocessing.

Which architecture change best meets these requirements?

Accepted Answer

Send EventBridge events to an SQS queue, configure a redrive policy to move messages to a dead-letter queue (DLQ) after a defined receive count, and make the Lambda processing idempotent.. It introduces an SQS queue between EventBridge and Lambda, which provides at-least-once processing through message visibility timeouts and retries. The redrive policy moves messages to a dead-letter queue (DLQ) after a defined receive count, ensuring bounded retries and preserving unprocessable events for later inspection and reprocessing. Making the Lambda idempotent prevents duplicate side effects from at-least-once delivery.

Answer

Invoke Lambda directly from EventBridge in asynchronous mode, and increase the Lambda timeout to reduce failures.

Answer

Use SNS topics with Lambda subscriptions, but remove all retry and DLQ configuration to minimize duplicate events.

Answer

Store failed events only in CloudWatch logs, and have operators manually copy log entries back into the database for reprocessing.

Question 3

A company runs the same public API in two regions (Region A and Region B), each fronted by an ALB. They want Route 53 to automatically route clients to the Region B API when Region A becomes unhealthy, with minimal configuration effort. Which Route 53 approach should they use?

Accepted Answer

Use Route 53 failover routing with health checks for each region’s endpoint.. Route 53 failover routing with health checks is the correct choice because it automatically directs traffic to a secondary endpoint (Region B) when the primary endpoint (Region A) fails a health check. This provides active-passive failover with minimal configuration, as Route 53 monitors the health of each ALB and updates DNS responses accordingly without manual intervention.

Answer

Use a single Route 53 A record that points only to Region A’s ALB and manually update it after failures.

Answer

Use Route 53 latency-based routing with separate records for each region.

Answer

Use weighted routing and set the Region B weight to 0 to ensure it is only used when needed.

Question 4

An order system receives events and uses a Lambda function to write each order into a database. During traffic spikes, the database sometimes throttles, and Lambda retries lead to occasional message loss in the event flow. The team wants buffering, automatic retries, and a way to isolate messages that repeatedly fail so they can be inspected later. What design change best meets this need?

Accepted Answer

Use Amazon SQS as a buffer between the event source and Lambda, with an SQS dead-letter queue (DLQ).. B is correct because Amazon SQS acts as a durable buffer between the event source and Lambda, absorbing traffic spikes and providing automatic retries via its visibility timeout mechanism. By attaching a dead-letter queue (DLQ) to the SQS queue, messages that repeatedly fail processing can be isolated for later inspection, preventing data loss and enabling debugging.

Answer

Send events directly from EventBridge to Lambda without any queue to simplify the flow.

Answer

Use SNS fan-out to multiple Lambda functions, but keep no retry logic and no DLQ.

Answer

Store events in an S3 bucket and trigger Lambda immediately after each upload, without using DLQs.

Question 5

A company runs its customer-facing web app on EC2 behind an Application Load Balancer. The database is Amazon RDS for PostgreSQL. The requirement is that if a single Availability Zone fails, the database must automatically fail over within the same AWS Region with minimal application changes. Which database setup best meets this requirement?

Accepted Answer

Deploy the RDS PostgreSQL instance as Multi-AZ with automatic failover enabled.. RDS Multi-AZ with automatic failover provides synchronous replication to a standby instance in a different Availability Zone. If the primary AZ fails, RDS automatically flips the DNS CNAME to the standby, resulting in minimal application changes (only a brief connection interruption). This meets the requirement for automatic failover within the same region without manual intervention.

Answer

Use an RDS single-AZ instance and periodically restore from automated backups if needed.

Answer

Create a read replica in a different AZ and use it only when the primary fails.

Answer

Use RDS with Multi-AZ disabled, but increase storage IOPS to prevent failover.

Question 6

A retail API runs on Amazon EC2 instances behind an Application Load Balancer and stores orders in an Amazon RDS for PostgreSQL database. A test that stopped one Availability Zone caused the API to return errors because all application servers were in the same AZ and the database was single-AZ. Which two changes should the architect make to continue serving traffic during a single-AZ failure? Select two.

Accepted Answer

Configure the Auto Scaling group to launch instances across private subnets in at least two Availability Zones.. Distributing EC2 instances across multiple Availability Zones via an Auto Scaling group ensures that if one AZ fails, the remaining AZs continue to serve traffic. Option D is correct because converting the RDS for PostgreSQL database to a Multi-AZ deployment provides a standby replica in a different AZ, enabling automatic failover and continued database availability during a single-AZ failure.

Answer

Increase the EC2 instance size and keep all application servers in the same subnet.

Answer

Replace the Application Load Balancer with a Network Load Balancer in a single Availability Zone.

Answer

Add an Amazon RDS read replica and point the application to the replica endpoint.

Question 7

A serverless order-ingestion API writes directly to a database. During traffic spikes, the database occasionally throttles, Lambda retries create duplicate order records, and some requests time out. Which two changes best improve buffering and safe retry behavior? Select two.

Accepted Answer

Put an Amazon SQS queue between the API and the database-processing function.. Inserting an SQS queue between the API Gateway and the Lambda function decouples the ingestion from the database write. During traffic spikes, SQS acts as a buffer, absorbing bursts and allowing the Lambda function to poll messages at a controlled rate, which prevents database throttling. Combined with a dead-letter queue, failed messages can be retried safely without overwhelming the database or creating duplicate records.

Answer

Increase the Lambda timeout and keep writing directly to the database.

Answer

Replace SQS with SNS so every request is delivered immediately to all subscribers.

Answer

Disable retries so failed writes are never duplicated.

Question 8

Your ecommerce app runs behind an Application Load Balancer (ALB) and uses an RDS database for orders. During an AZ impairment in us-east-1, customers report that checkout takes several minutes to recover. The current design places EC2 instances only in private subnets of AZ-a, while the ALB spans multiple subnets. The RDS DB instance is Multi-AZ. Management wants automatic recovery within the same Region.

Which change best addresses the issue with minimal operational overhead?

Accepted Answer

Move the EC2 instances into Auto Scaling Groups that span private subnets in at least two AZs, keeping the ALB spanning those subnets.. The current design has a single point of failure: all EC2 instances are in one Availability Zone (AZ-a). During an AZ impairment, those instances become unreachable, causing the checkout process to fail until the impairment ends or manual intervention occurs. By placing EC2 instances in an Auto Scaling Group spanning at least two AZs, the application can automatically recover by launching new instances in a healthy AZ, while the ALB distributes traffic across the surviving AZs. This minimizes operational overhead as Auto Scaling handles instance replacement automatically.

Answer

Switch from RDS Single-AZ to RDS Multi-AZ, keeping the EC2 instances in only AZ-a because failover will still reach them.

Answer

Terminate the ALB and use a Network Load Balancer (NLB) in front of the existing single-AZ EC2 instances.

Answer

Add more EC2 instances in AZ-a and increase the ALB health check thresholds to avoid unnecessary replacements during impairments.

Question 9

Your media processing pipeline writes original uploads to an S3 bucket and later generates derivative files. An operator accidentally deletes a subset of original uploads in production. You need to (1) restore the deleted objects with minimal data loss and (2) protect against both regional disasters and future operator mistakes. The company requires recovery even if objects are deleted and later overwritten.

What is the most effective change to meet these requirements?

Accepted Answer

Enable S3 versioning on the bucket and configure cross-Region replication so previous versions are available after regional loss and accidental deletion.. Enabling S3 Versioning preserves all object versions, including deleted markers and overwritten objects, allowing recovery from accidental deletions. Cross-Region Replication (CRR) replicates both current and previous versions to a secondary region, providing protection against regional disasters. This combination ensures that even if objects are deleted and later overwritten, the original versions remain recoverable in both the source and destination buckets.

Answer

Move all objects to S3 Glacier Instant Retrieval and apply a lifecycle policy to keep only the latest object copy.

Answer

Use S3 server-side encryption with KMS keys and rely on access logs to manually recover the deleted objects.

Answer

Enable S3 bucket policies that deny DeleteObject, but do not enable versioning or replication.

Question 10

Based on the exhibit, a web application must stay available if one Availability Zone fails. What is the best change to improve resilience?

Accepted Answer

Add a subnet in another Availability Zone to the Auto Scaling group and keep the ALB spanning both AZs.. Adding a subnet in another Availability Zone (AZ) to the Auto Scaling group and keeping the ALB spanning both AZs ensures that if one AZ fails, the ALB can route traffic to healthy instances in the other AZ. This is the standard pattern for building multi-AZ resilient architectures with Auto Scaling and ALB, as it eliminates the single point of failure at the AZ level.

Answer

Increase the desired capacity to 8 instances in the same subnet.

Answer

Replace the Application Load Balancer with a Network Load Balancer.

Answer

Move the instances to a larger instance type with more CPU and memory.

Question 11

Match the disaster recovery strategy to the recovery posture it best fits for a Regional outage.

Accepted Answer

Backup & Restore: RPO hours, RTO hours. The pairs match disaster recovery strategies to their typical recovery posture for a regional outage, based on AWS Well-Architected Framework and common DR patterns.

Answer

Pilot Light: RPO seconds, RTO minutes

Answer

Warm Standby: RPO minutes, RTO minutes

Question 12

A global application experiences frequent writes and must survive a full Regional outage with near-zero data loss. The product team also requires that users can continue to write during the incident using the closest Region. Which approach is most aligned with these requirements?

Accepted Answer

Use an active/active design with multi-Region data replication (for example, global tables for the write-heavy datastore) and route traffic to multiple Regions based on health and latency.. An active/active design with multi-Region data replication, such as DynamoDB global tables, allows writes to occur in any Region and replicates data asynchronously across Regions with sub-second latency. This ensures near-zero data loss (RPO of seconds) and continuous write availability during a full Regional outage, while Route 53 latency-based routing directs users to the closest healthy Region.

Answer

Use warm standby with periodic backups of the primary write datastore every 24 hours.

Answer

Use pilot light where the secondary Region runs only infrastructure templates and starts data replication only after detecting failure.

Answer

Use a single-writer model in one Region and deploy read-only replicas in the other Region for continuity.

Question 13

A company uses Amazon RDS for a PostgreSQL database powering a customer-facing application. The application’s availability depends on fast database failover with minimal manual intervention. The RDS instance currently runs as a single-AZ deployment in one DB subnet group. Which change most directly meets the goal?

Accepted Answer

Enable Multi-AZ for the RDS DB instance so AWS manages a standby in another Availability Zone with automatic failover.. Enabling Multi-AZ for the RDS DB instance creates a synchronous standby replica in a different Availability Zone. AWS automatically handles failover to the standby with no manual intervention required, meeting the goal of fast database failover with minimal manual intervention.

Answer

Create a read replica in a different Availability Zone and configure the application to fail over manually.

Answer

Switch the database to use EBS snapshots more frequently and restore in case of failure.

Answer

Pin the DB to a specific instance type with higher CPU credits to prevent CPU-related disconnects.

Question 14

An order processing workflow uses Amazon SQS as the decoupling layer between a producer and a consumer Lambda function. The consumer intermittently fails due to a downstream dependency. The team has observed that certain “poison” messages keep being retried repeatedly and prevent other messages from being processed efficiently. Which SQS configuration most directly addresses this issue?

Accepted Answer

Configure a redrive policy with a dead-letter queue (DLQ) and set an appropriate visibility timeout greater than the maximum processing time.. Configuring a redrive policy with a dead-letter queue (DLQ) allows messages that exceed a specified maximum receive count to be moved to the DLQ, isolating poison messages. Setting the visibility timeout greater than the maximum processing time ensures the consumer has enough time to process each message before it becomes visible again, preventing premature retries. This directly addresses the issue of poison messages blocking the queue and degrading throughput.

Answer

Set the SQS queue’s retention period to 10 years and rely on application retries to eventually succeed.

Answer

Increase visibility timeout to a very large value and avoid dead-letter queues to keep ordering stable.

Answer

Switch the queue to FIFO and remove retries in the Lambda event source mapping entirely.

Question 15

A company runs a stateful analytics workload on EC2 instances that use EBS volumes. The data must be restorable in another Region after a major outage, with frequent point-in-time recovery. Which approach provides the most suitable replication mechanism for the EBS-backed data?

Accepted Answer

Create scheduled EBS snapshots and copy them to another Region, then restore the volumes from those snapshots during recovery.. Scheduled EBS snapshots provide point-in-time recovery and can be copied to another Region for cross-region disaster recovery. When a major outage occurs, you can restore EBS volumes from those snapshots in the target Region, meeting the requirement for frequent restorable backups. This approach is native to AWS, cost-effective, and supports the stateful analytics workload without architectural changes.

Answer

Enable EBS multi-attach to spread the workload across AZs and replicate snapshots automatically between Regions.

Answer

Use RDS read replicas in another Region and keep the analytics dataset in an RDS instance only.

Answer

Rely on instance store for durability and copy only AMIs across Regions.