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

Question 1

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.

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

Accepted Answer

Configure the Auto Scaling group to launch instances across private subnets in at least two Availability Zones.. 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 2

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 3

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 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.

Question 4

A media company stores daily financial exports in Amazon S3. The files must be protected against accidental overwrite or deletion, and the business also wants a second copy in another Region for recovery after a regional outage. Which two actions should the architect take? Select two.

Accepted Answer

Enable bucket versioning on the S3 bucket.. Enabling S3 Versioning on the bucket protects objects from accidental overwrite or deletion by preserving previous versions of each object. When versioning is enabled, a delete marker is placed instead of permanently removing the object, and overwrites create a new version while retaining the old one. This directly meets the requirement to guard against accidental data loss.

Answer

Turn on S3 Transfer Acceleration for the bucket.

Answer

Use only lifecycle policies to move objects to Glacier.

Answer

Enable S3 Block Public Access on the bucket.

Question 5

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 buffers the requests, allowing the Lambda function to poll at a controlled rate, which prevents database throttling. Additionally, SQS provides built-in retry logic with a visibility timeout, so failed messages are automatically retried without creating duplicate order 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 6

A SaaS platform serves an API using two regional deployments: us-east-1 (primary) and us-west-2 (secondary). Each region has its own ALB. The business requires automated DNS-based failover when the primary region becomes unhealthy, and they do not want manual DNS changes during incidents. 

Which Route 53 configuration is the best match?

Accepted Answer

Use Route 53 failover routing with a primary record pointing to the us-east-1 ALB and a secondary record pointing to the us-west-2 ALB, each using health checks.. Route 53 failover routing is designed for active-passive configurations where traffic must automatically shift to a secondary endpoint when the primary fails. By attaching health checks to the primary record (us-east-1 ALB), Route 53 can detect regional unavailability and automatically route traffic to the secondary record (us-west-2 ALB) without manual intervention. This meets the requirement for DNS-based failover without manual DNS changes during incidents.

Answer

Create a single Route 53 record using weighted routing across both ALBs with weights adjusted manually during an incident.

Answer

Use latency-based routing so Route 53 always selects the fastest region; health checks are unnecessary because client latency reflects availability.

Answer

Use a single A record with a static IP address that points to a NAT gateway, and update that IP during failure events.

Question 7

A fintech startup uses AWS to run a web API and a PostgreSQL database. They must meet an RPO of 15 minutes and an RTO of 2 hours for a Region-wide disaster. Budget allows running a small, always-on set of infrastructure in a secondary Region, but not full production capacity. The team wants a DR approach that is regularly testable without large manual effort.

Which disaster recovery strategy is the best fit?

Accepted Answer

Warm standby: keep a scaled-down application environment and database replication active in the secondary Region, using automated failover controls.. Warm standby (B) is the best fit because it maintains a scaled-down but fully functional application environment in the secondary Region with active database replication, meeting the RPO of 15 minutes (via synchronous or near-synchronous replication like PostgreSQL streaming replication) and RTO of 2 hours (via automated failover controls such as Route 53 health checks and AWS Lambda automation). This approach allows regular testing without large manual effort by simply promoting the standby environment, and the budget constraint is satisfied by running only minimal compute resources (e.g., smaller EC2 instances) in the secondary Region.

Answer

Pilot light: replicate databases and store backups, keep only minimal infrastructure in the secondary Region, and scale up fully during failover.

Answer

Backup and restore only: rely on daily automated backups and restore into the secondary Region during an incident.

Answer

Multi-site active-active: run both Regions at full capacity and route live traffic to both simultaneously.

Question 8

A company runs a customer portal on an Amazon Aurora PostgreSQL cluster. The application currently connects directly to the writer instance endpoint and keeps long-lived connections open. During a maintenance failover, writes fail until clients are restarted. The team wants the application to reconnect to the correct Aurora endpoint automatically and reduce user-visible write interruptions.

Which change is most likely to achieve this?

Accepted Answer

Use the Aurora cluster endpoint for write traffic, use the reader endpoint for read-only traffic, and implement connection retry or reconnect logic on failover.. The Aurora cluster endpoint automatically points to the current writer instance, so using it for write traffic ensures that after a failover, new writes are directed to the new writer without needing to change the connection string. Implementing connection retry or reconnect logic in the application is essential because the existing long-lived connections will be broken during failover; the application must detect the failure and re-establish connections to the cluster endpoint to resume writes seamlessly.

Answer

Keep using the original writer instance endpoint so the database host name never changes during failover.

Answer

Convert the Aurora cluster to Single-AZ so there is only one database node to connect to.

Answer

Place Route 53 in front of the database and manually update DNS records whenever failover occurs.

Question 9

A team uses an S3 bucket to store important customer-generated exports. They need protection against accidental overwrites and also want copies of the data in another AWS Region for disaster recovery. Which S3 configuration best satisfies both requirements?

Accepted Answer

Enable S3 versioning and configure Cross-Region Replication to a destination bucket in another Region.. Enabling S3 versioning protects against accidental overwrites by preserving previous versions of objects, and configuring Cross-Region Replication (CRR) automatically replicates objects to a destination bucket in another AWS Region, providing disaster recovery. This combination meets both requirements without manual intervention.

Answer

Enable S3 lifecycle policies to automatically move objects to Glacier after 30 days only.

Answer

Disable all versioning and rely on AWS Backup to restore objects from a scheduled backup window.

Answer

Enable S3 Block Public Access and SSE-S3 encryption, without using versioning or replication.

Question 10

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.. Placing both the ALB and the Auto Scaling group across multiple subnets in at least two Availability Zones ensures that if one AZ becomes unavailable, the ALB can route traffic to healthy instances in the remaining AZs, and the Auto Scaling group can automatically launch replacement instances in the other AZs. This directly provides automatic failover for the compute layer within a single Region 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 11

A SaaS application is deployed in us-east-1 and us-west-2 behind separate ALBs. The business wants DNS to send new clients to the primary Region when it is healthy and automatically fail over to the secondary Region when the primary endpoint is unhealthy. Which two Route 53 settings are required? Select two.

Accepted Answer

Use a failover routing policy with a primary and secondary record.. A failover routing policy is correct because it allows you to designate one record as primary and another as secondary. Route 53 will route traffic to the primary record as long as it is healthy, and automatically fail over to the secondary record when the primary becomes unhealthy. This directly meets the requirement to send new clients to the primary region when healthy and fail over automatically.

Answer

Use weighted routing with a 50/50 traffic split between both Regions.

Answer

Use latency-based routing so clients always choose the fastest Region.

Answer

Use a geolocation policy without health checks.

Question 12

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?

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 13

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 14

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 15

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.