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

Question 1

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?

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

Accepted Answer

Configure an ElastiCache Redis replication group with automatic failover across multiple Availability Zones.. 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 during maintenance events without interruption, as the failover is transparent to the application.

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 2

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.. 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, enabling recovery from a full Region outage. With an RPO of about 1 hour, CRR meets this requirement as replication typically completes within minutes to a few hours, and versioning ensures point-in-time recovery of previous object states.

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 3

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.. It directly addresses the single point of failure: the ASG only launches instances in one AZ, so when that AZ fails, the ALB has no healthy targets to route traffic to, causing timeouts. By configuring the ASG to span at least two AZs, the ALB can distribute traffic to healthy instances in the remaining AZ during maintenance, ensuring high availability. The ALB health check must target an application-ready path (e.g., /health) to accurately detect instance health and avoid routing requests to impaired instances.

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 4

A web app runs on an EC2 Auto Scaling group behind an Application Load Balancer (ALB). The ALB is configured with health checks and the ASG spans three subnets in three Availability Zones. During an AZ outage, monitoring shows the number of healthy instances drops sharply and never returns to the original capacity until the ASG is manually adjusted. What change most directly improves resilience so capacity returns automatically during an AZ failure?

Accepted Answer

Configure the ASG to use the ALB target-group health checks (ELB/target-group health) and ensure the ASG has at least two subnets in different Availability Zones that remain available for instance placement.. Configuring the ASG to use ALB target-group health checks (ELB health checks) ensures that the ASG replaces instances that fail the ALB's health checks, including those in an impaired AZ. By also ensuring the ASG has at least two subnets in different AZs that remain available, the ASG can launch replacement instances in the healthy AZs when one AZ fails, automatically restoring capacity without manual intervention.

Answer

Reduce the ASG desired capacity by 1 and rely on the ALB to route traffic to fewer instances during the outage.

Answer

Move the ALB to only one subnet so health checks and routing remain consistent during the outage.

Answer

Add an S3 event trigger to terminate unhealthy instances so the ASG can scale back out using its scheduled actions.

Question 5

A company hosts a public API using two AWS regions behind a single custom domain. Route 53 is configured with latency-based routing and health checks. During a regional outage, application metrics confirm the primary API is unhealthy, but clients still resolve to the primary region for most requests. Which DNS configuration change will most directly ensure automatic failover to the secondary region when the primary fails?

Accepted Answer

Switch to Route 53 failover routing: configure the primary record with the primary health check and the secondary record with the secondary failover health check.. Route 53 failover routing with health checks explicitly directs traffic to the secondary region when the primary health check fails. This ensures automatic failover at the DNS level, whereas latency-based routing does not guarantee failover even with health checks—it only reduces latency and may still return unhealthy records if no healthier alternative exists.

Answer

Change the record type to A/AAAA alias with an active-active routing policy so both regions always receive equal traffic.

Answer

Keep latency-based routing but shorten the health check interval to 5 seconds.

Answer

Use geolocation routing so requests from each country route to the nearest region.

Question 6

An orders service publishes payment instructions to an Amazon SQS queue. The downstream consumer sometimes times out while processing a message. After the message becomes visible again, the consumer may process the same instruction more than once and occasionally creates duplicate orders. The team needs a resiliency-focused design that prevents duplicates from creating double-charges, even if the same message is processed multiple times. What is the best architectural change?

Accepted Answer

Make the consumer idempotent by using an idempotency key from the payment instruction (for example, a unique transaction/payment ID) and storing processing results with conditional writes so repeated deliveries do not create a second order.. Making the consumer idempotent ensures that processing the same payment instruction multiple times does not result in duplicate orders or double charges. By using a unique idempotency key (e.g., transaction ID) and conditional writes (e.g., DynamoDB conditional put or database INSERT ... ON CONFLICT DO NOTHING), the consumer can safely handle repeated message deliveries without side effects. This directly addresses the resiliency requirement without relying on SQS guarantees, which standard queues do not provide for exactly-once delivery.

Answer

Rely on SQS to guarantee exactly-once delivery for standard queues and remove all duplicate-handling logic in the consumer.

Answer

Increase the SQS visibility timeout to the maximum value so the consumer never retries the message.

Answer

Change the queue to SNS with a fan-out subscription so each consumer gets a separate copy, ensuring processing is sequential and duplicate-free.

Question 7

An internal-facing application is available in two AWS regions (Region 1 and Region 2). Each region has its own Application Load Balancer (ALB) and target group. The company uses an AWS Route 53 private hosted zone to route clients to Region 1 by default, but it must automatically fail over to Region 2 when Region 1’s ALB is unhealthy. Which Route 53 design best meets this requirement?

Accepted Answer

Use failover routing with two alias A records for the same name: one PRIMARY and one SECONDARY, both pointing to each region’s ALB; attach the health check to the PRIMARY record.. Route 53 failover routing with a PRIMARY and SECONDARY alias record allows automatic failover when the health check attached to the PRIMARY record fails. The health check monitors Region 1's ALB, and upon failure, Route 53 returns the SECONDARY record's IP (Region 2's ALB) to clients. This design meets the requirement for automatic failover without manual intervention.

Answer

Use latency-based routing with two alias records; Route 53 will automatically shift traffic away from the unhealthy region.

Answer

Use weighted routing with weights 100/0 and update weights manually after detecting failures.

Answer

Use geolocation routing with a single alias record for Region 1, and enable EDNS Client Subnet to detect unhealthy endpoints.

Question 8

A web application runs on an Auto Scaling group behind an Application Load Balancer. The business wants the service to keep running if one Availability Zone goes down. Which two changes should you make? Select two.

Accepted Answer

Place the Auto Scaling group in subnets across at least two Availability Zones.. Placing the Auto Scaling group in subnets across at least two Availability Zones ensures that if one AZ fails, the Auto Scaling group can still launch instances in the remaining healthy AZ(s). This is a fundamental pattern for high availability, as the Auto Scaling group distributes instances across the specified subnets, and if an entire AZ becomes unavailable, instances in other AZs continue to serve traffic.

Answer

Increase the instance size so each server can handle more traffic alone.

Answer

Disable ALB health checks so instances stay registered longer.

Answer

Run the whole stack in one Availability Zone for simpler networking.

Question 9

A production Amazon RDS database must continue serving the application if the primary DB instance fails. The application should reconnect automatically without hard-coding a new IP address. Which two actions should you take? Select two.

Accepted Answer

Create an RDS Multi-AZ deployment for the database.. A is correct because an RDS Multi-AZ deployment automatically provisions and maintains a synchronous standby replica in a different Availability Zone. If the primary DB instance fails, Amazon RDS automatically fails over to the standby, typically within 60–120 seconds, without requiring manual intervention. This ensures high availability and continuity for the production database.

Answer

Disable automated backups to reduce the time needed for failover.

Answer

Use a single-AZ deployment so the standby is not split across Zones.

Answer

Replace the database with an Amazon S3 bucket and store rows as objects.

Question 10

A company hosts an internal API in two AWS Regions. Traffic must automatically switch to the secondary Region when the primary Region's endpoint is unhealthy. Which two Route 53 settings are required? Select two.

Accepted Answer

Use a failover routing policy for the DNS record.. A failover routing policy is required because it allows Route 53 to automatically route traffic from a primary resource to a secondary resource when the primary is unhealthy. This is the only routing policy that supports active-passive failover across two AWS Regions. Without this policy, Route 53 would not know which endpoint to consider primary or how to switch traffic upon failure.

Answer

Use geolocation routing so users are always sent to the closest Region.

Answer

Use a private hosted zone to expose the API to the internet.

Answer

Set the TTL to zero and skip health checks to make failover faster.

Question 11

A batch processing job can be interrupted and restarted from checkpoints. The business wants to lower compute cost while still keeping the workload resilient to interruptions. Which two choices are best? Select two.

Accepted Answer

Run the workload on Amazon EC2 Spot Instances.. Amazon EC2 Spot Instances offer significant cost savings (up to 90% compared to On-Demand) and are ideal for fault-tolerant, stateless batch processing jobs that can be interrupted and restarted from checkpoints. The workload's ability to resume from checkpoints makes it resilient to Spot Instance interruptions, aligning perfectly with the business goal of lowering compute costs while maintaining resilience.

Answer

Use a single On-Demand instance in one Availability Zone only.

Answer

Disable automatic replacement so the job is never restarted.

Answer

Keep all intermediate state only in instance memory.

Question 12

Your web tier runs on an EC2 Auto Scaling group behind an Application Load Balancer (ALB). You currently deploy both the ALB and the Auto Scaling group in only two Availability Zones (AZs). One AZ fails. What is the best configuration change to improve resilience?

Accepted Answer

Add a third Availability Zone so the ALB and Auto Scaling group span at least three AZs.. Adding a third Availability Zone (AZ) ensures that the Application Load Balancer (ALB) and Auto Scaling group (ASG) can continue to route traffic and maintain capacity even if one AZ fails. With only two AZs, a single AZ failure reduces the fleet by 50% and may cause the ALB to lose the minimum healthy hosts required to serve traffic. Spreading across three AZs provides a higher resilience margin, as the remaining two AZs can absorb the load while the failed AZ recovers.

Answer

Reduce health check timeouts so instances are replaced sooner in the failed AZ.

Answer

Enable instance scale-in protection to stop the ASG from terminating unhealthy instances.

Answer

Switch the ALB to an internal Network Load Balancer (NLB) to avoid cross-AZ traffic.

Question 13

A company wants a disaster recovery setup for a web application. They need relatively quick recovery, but they can't afford running full production in the secondary location at all times. Which option best matches this requirement?

Accepted Answer

Warm standby: run a minimal but functional version of the application and supporting services in the secondary location, and scale up during a failure.. Warm standby (Option B) is correct because it runs a minimal but functional version of the application in the secondary region, allowing for faster recovery than a pilot light while avoiding the cost of full production. During a failure, you scale up the standby environment to handle production traffic, meeting the requirement for relatively quick recovery without the expense of active-active.

Answer

Pilot light: keep only essential infrastructure in the secondary location and scale up the application during a failure.

Answer

Active-active: run full production in both the primary and secondary locations at the same time.

Answer

Backup and restore only: rely on periodic backups and restore the application after a failure.

Question 14

A fintech company needs a disaster recovery design for a web application in two Regions. The business requires an RPO of 15 minutes and an RTO under 2 hours, but it cannot afford to keep a full production stack running in both Regions all the time. Which two DR strategies best fit the requirement? Select two.

Accepted Answer

Pilot light with critical data and minimal services pre-staged in the secondary Region.. A pilot light strategy is correct because it pre-stages only critical data (e.g., database replication) and minimal core services (e.g., a small EC2 instance or RDS standby) in the secondary Region, which can be scaled up to full production within the RTO of under 2 hours. The RPO of 15 minutes is achievable by using synchronous or near-synchronous replication (e.g., Amazon RDS Multi-AZ cross-Region or DynamoDB global tables) to keep data loss minimal. This approach avoids the cost of a full production stack while meeting the recovery objectives.

Answer

Active-active deployment with full production capacity in both Regions.

Answer

Backup-and-restore only, with no pre-provisioned resources in the secondary Region.

Answer

Single-Region deployment with Multi-AZ only, because that already covers disaster recovery.

Question 15

A transactional application uses Amazon RDS for MySQL in a single Availability Zone. The team wants the database to fail over automatically if the primary DB instance becomes unavailable, and they want the application to recover with minimal code changes. Which two actions should they take? Select two.

Accepted Answer

Convert the database to an RDS Multi-AZ deployment.. RDS Multi-AZ automatically synchronously replicates data to a standby instance in a different Availability Zone. If the primary fails, RDS automatically fails over to the standby, typically within 60–120 seconds, with no manual intervention required. This meets the requirement for automatic failover with minimal code changes.

Answer

Add a read replica and promote it manually during an outage.

Answer

Store the current DB instance IP address in the application configuration file.

Answer

Rely on nightly snapshots because they provide automatic failover to another Availability Zone.