SAA-C03 Design Resilient Architectures Practice Test 3 — 15 Questions

Question 1

A team wants a web application to keep serving traffic if one Availability Zone fails. Match each architecture element to the resilience behavior it provides.

Question 2

Based on the exhibit, the database must fail over automatically if the primary Availability Zone goes down. Which solution should the architect choose?

Accepted Answer

Convert the database to a Multi-AZ RDS deployment.. A Multi-AZ RDS deployment automatically synchronously replicates data to a standby instance in a different Availability Zone. If the primary AZ fails, Amazon RDS automatically performs a failover to the standby, ensuring high availability without manual intervention. This meets the requirement for automatic failover when the primary AZ goes down.

Answer

Create a read replica in the same Availability Zone as the primary database.

Answer

Increase the backup retention period to 35 days.

Answer

Move the database to an EC2 instance with an attached EBS volume.

Question 3

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, which directly meets 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 4

A stateless web API runs on EC2 instances behind an Application Load Balancer (ALB). The Auto Scaling group (ASG) currently uses subnets from only one Availability Zone, even though the ALB spans two Availability Zones. During maintenance of that single AZ, the ALB remains up but clients see timeouts because there are no healthy targets. Which change most directly improves resilience against an AZ failure?

Accepted Answer

Update the ASG to launch instances across subnets in at least two Availability Zones and ensure ALB health checks target an application-ready path.. The most direct fix for AZ failure resilience is to distribute the ASG across multiple Availability Zones. With the ALB already spanning two AZs, if the ASG only launches instances in one AZ, a failure of that AZ leaves the ALB with zero healthy targets, causing timeouts. By configuring the ASG to launch instances in at least two AZs and setting ALB health checks to an application-ready path, the ALB can route traffic to healthy instances in the surviving AZ, maintaining availability.

Answer

Keep the ASG in one subnet/AZ, but enable ALB stickiness to reduce session interruption.

Answer

Add a NAT gateway in the public subnets so instances can reach the internet during maintenance events.

Answer

Create a second ALB in the same Availability Zone and route traffic using DNS failover.

Question 5

A caching layer uses Amazon ElastiCache for Redis in front of a stateless web service. The service must continue to read cached responses during maintenance events and should automatically fail over to another node if one AZ becomes impaired. Which design change best satisfies this requirement?

Accepted Answer

Configure an ElastiCache Redis replication group with automatic failover across multiple Availability Zones.. Option B is correct because an ElastiCache Redis replication group with automatic failover across multiple Availability Zones ensures that if the primary node or its AZ becomes impaired, a read-replica in another AZ is automatically promoted to primary. This allows the stateless web service to continue reading cached responses without interruption, satisfying both the maintenance and AZ impairment requirements.

Answer

Deploy a single-node Redis cluster and rely on application-level retries when cache misses occur.

Answer

Move the cache into the VPC but keep it in one Availability Zone to reduce network latency.

Answer

Use a Memcached cluster and configure only client-side connection pooling without failover support.

Question 6

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 backups of EBS volumes, which can be copied to another Region using the cross-Region snapshot copy feature. During recovery, you restore volumes from those snapshots in the target Region, ensuring the data is restorable after a major outage. This approach meets the requirements for frequent point-in-time recovery and cross-Region durability.

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.

Question 7

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.. Option C is correct because configuring a redrive policy with a dead-letter queue (DLQ) allows messages that repeatedly fail processing to be moved out of the main queue after a specified number of receive attempts. Setting an appropriate visibility timeout greater than the maximum processing time ensures that messages are not made visible again before the consumer finishes processing, preventing premature retries. This directly isolates poison messages so they no longer block the processing of other messages in the queue.

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 8

A media company stores original uploads in an S3 bucket. They must recover from accidental overwrites/deletes and also recover quickly from a full Region outage. The required RPO is about 1 hour. Which configuration best meets these requirements?

Accepted Answer

Enable S3 versioning and configure cross-Region replication to a bucket in another Region.. Option C is correct because enabling S3 versioning protects against accidental overwrites and deletes by preserving all object versions, while cross-Region replication (CRR) asynchronously replicates objects to a bucket in another Region, providing recovery from a full Region outage. With versioning enabled, CRR replicates both current and previous object versions, meeting the ~1-hour RPO (typically within minutes for new objects) and ensuring data durability across Regions.

Answer

Enable an S3 lifecycle policy to transition objects to Glacier after 7 days without enabling versioning.

Answer

Enable S3 cross-Region replication (CRR) but leave the bucket without versioning enabled.

Answer

Rely on frequent EBS snapshots of a temporary cache used during uploads.

Question 9

An ECS service runs on EC2 instances and is fronted by an ALB. The ALB spans two Availability Zones, and the ECS service desired count is 2 tasks. The underlying EC2 capacity uses an Auto Scaling group (ASG) with min size set to 1, and the ASG also spans only one subnet in practice. What is the most effective change to meet the requirement that the service continues during a single-AZ instance loss?

Accepted Answer

Increase ASG min size to at least 2 and ensure the ASG uses subnets in at least two Availability Zones.. The current architecture has a single point of failure because the Auto Scaling group (ASG) spans only one subnet (one Availability Zone). If that AZ fails, all EC2 instances are lost, and the ECS service cannot run any tasks. Increasing the ASG min size to at least 2 and configuring it to use subnets in at least two AZs ensures that EC2 instances are distributed across AZs, allowing the ECS service to maintain at least one task in the surviving AZ during a single-AZ failure.

Answer

Set the ECS deployment configuration to maximum percent 100 so tasks replace instances faster during rollouts.

Answer

Enable ALB connection draining longer than expected so existing connections survive longer during an AZ event.

Answer

Reduce task memory reservations to pack both tasks onto a single EC2 instance.

Question 10

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.. Option A is correct because it introduces an SQS queue between EventBridge and Lambda, which provides a durable buffer for events. The redrive policy moves events to a dead-letter queue (DLQ) after a defined number of failed processing attempts, ensuring bounded retries and preserving unprocessable events for later inspection and reprocessing. Making the Lambda idempotent guarantees at-least-once processing even if duplicate events occur.

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 11

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.. Option B is correct because distributing EC2 instances across private subnets in at least two Availability Zones (AZs) ensures that if one AZ fails, the Auto Scaling group can continue serving traffic from instances in the remaining AZs. This eliminates the single point of failure for the application tier. Option D is correct because converting the RDS for PostgreSQL database to a Multi-AZ deployment automatically provisions a standby replica in a different AZ, enabling automatic failover during an AZ outage and preserving database availability.

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 12

An engineering team deploys a stateless web API on EC2 using an Auto Scaling group and an Application Load Balancer (ALB). During a recent test, they noticed that when one Availability Zone was unavailable, traffic failed until new instances were manually launched. Which change most directly improves automatic failover for the compute layer within a single Region?

Accepted Answer

Ensure the ALB and Auto Scaling group span multiple subnets in at least two Availability Zones.. Option B is correct because an Application Load Balancer (ALB) and Auto Scaling group must span multiple subnets in at least two Availability Zones (AZs) to provide automatic failover. When one AZ becomes unavailable, the ALB automatically reroutes traffic to healthy targets in the remaining AZs, and the Auto Scaling group can launch replacement instances in the surviving AZs. This architecture ensures that the compute layer remains available without manual intervention.

Answer

Place the Auto Scaling group in only one subnet so instance launches are simpler.

Answer

Increase the target group deregistration delay to allow old instances to stay longer.

Answer

Use a Network Load Balancer, but keep all subnets in a single Availability Zone.

Question 13

A customer portal must recover from a regional outage within a few hours. The business wants lower ongoing cost than a fully active second Region and does not want to rebuild everything from scratch during the outage. Which two DR patterns best fit that goal? Select two.

Accepted Answer

Pilot light. Pilot light is correct because it maintains a minimal core infrastructure (e.g., database, networking) in the secondary Region that can be quickly scaled up during a disaster, meeting the recovery time objective (RTO) of a few hours while keeping ongoing costs lower than a fully active second Region. It avoids rebuilding everything from scratch by having critical data and configurations already in place, allowing compute resources to be launched on demand.

Answer

Backup and restore

Answer

Multi-site active-active

Answer

Single-AZ deployment

Question 14

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.. Option A is correct because enabling S3 Versioning preserves all object versions, including overwrites and deletions (which become delete markers), allowing you to restore deleted objects by removing the delete marker. Cross-Region Replication (CRR) replicates both current and previous versions to a secondary Region, protecting against regional disasters. Together, they ensure recovery even if objects are deleted and later overwritten, meeting all requirements.

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 15

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.. Option B is correct because RDS Multi-AZ for PostgreSQL automatically provisions and maintains a synchronous standby replica in a different Availability Zone. If the primary AZ fails, Amazon RDS automatically fails over to the standby, typically within 60–120 seconds, with no changes required to the application's connection string (the DNS name remains the same). This meets the requirement for minimal application changes and automatic failover within the same Region.

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.