SAA-C03 Design Resilient Architectures — Timed 20 Questions

Question 1

A web application uses pooled JDBC connections to an Amazon Aurora cluster using the writer endpoint. During an Aurora planned failover, monitoring shows a short spike in failed requests. The Aurora cluster writer endpoint remains the same, but many existing pooled connections briefly fail. The application retries aggressively and overloads the new writer during the transition.

Which design change will most improve application resilience during Aurora failovers without requiring application redeployment?

Accepted Answer

Add an RDS Proxy between the application and Aurora to manage database connections across failovers.. RDS Proxy sits between the application and the Aurora cluster, maintaining a warm connection pool to the database. During a failover, RDS Proxy transparently reconnects to the new writer instance without dropping the application's existing connections, eliminating the spike in failed requests and preventing the aggressive retry storm that overloads the new writer. This requires no code changes or redeployment, as the application simply connects to the proxy endpoint instead of the cluster endpoint.

Answer

Change the Aurora cluster to Single-AZ to reduce failover events.

Answer

Increase the application thread count so more requests can be served while connections reconnect.

Answer

Pin all database traffic to a specific instance hostname instead of the writer cluster endpoint.

Question 2

A payments platform requires disaster recovery across Regions. Requirements: RPO of 15 minutes and RTO of about 1 hour. The business cannot afford full duplicate capacity in both Regions all the time, but the team wants automated readiness so failover is mostly operationally guided rather than a slow rebuild. Which DR strategy is the best fit?

Accepted Answer

Warm standby, keeping core infrastructure and a partially provisioned environment ready in the secondary Region with frequent data replication.. Warm standby is the best fit because it maintains a partially provisioned environment in the secondary Region with core infrastructure (e.g., a smaller EC2 Auto Scaling group, a standby database with synchronous or asynchronous replication) and frequent data replication, enabling an RPO of 15 minutes and an RTO of about 1 hour. This approach balances cost and automated readiness, as the team can scale up the standby environment during failover without the expense of full duplicate capacity, while still meeting the recovery objectives through automated replication (e.g., Amazon RDS Multi-AZ cross-Region or DynamoDB global tables).

Answer

Backup and restore only, relying on scheduled snapshots and manual restores during incidents.

Answer

Pilot light, keeping only minimal infrastructure in the secondary Region and starting full services after failover.

Answer

Active/active, routing production traffic to both Regions continuously and accepting dual-region complexity.

Question 3

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.

Accepted Answer

Application Load Balancer (ALB): Distributes incoming traffic across healthy targets in multiple Availability Zones.. These pairs match architecture elements with their resilience behaviors for surviving an Availability Zone failure, focusing on AWS services that provide high availability and fault tolerance.

Answer

Application Load Balancer (ALB): Automatically replaces failed instances across Availability Zones.

Answer

Auto Scaling group: Distributes incoming traffic across healthy instances in multiple Availability Zones.

Question 4

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 5

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 6

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 7

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 places EC2 instances only in AZ-a, so when that AZ becomes impaired, all compute capacity is lost, causing checkout to fail until the impairment ends or manual intervention occurs. By moving EC2 instances into Auto Scaling Groups spanning at least two AZs, the application gains automatic recovery within the same Region because the ALB can route traffic to healthy instances in the remaining AZs. This change minimizes operational overhead because Auto Scaling automatically replaces failed instances and maintains desired capacity across AZs, while the ALB’s health checks ensure traffic is only sent to healthy targets.

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 8

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 the secondary (Region B) endpoint when the primary (Region A) endpoint fails a health check. This provides automated DNS failover with minimal configuration effort, as Route 53 monitors the health of each ALB endpoint and updates DNS responses accordingly.

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 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

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 (e.g., PostgreSQL streaming replication or AWS DMS with ongoing replication). Automated failover controls (e.g., Route 53 health checks and Lambda automation) can achieve the RTO of 2 hours by scaling up the standby environment, and the always-on infrastructure allows regular, low-effort testing of the failover process without manual intervention.

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 11

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 protects objects from accidental overwrite or deletion by preserving previous versions. When a file is overwritten or deleted, the original version is retained, allowing recovery. This directly addresses the requirement to guard against data loss from user or application errors.

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 12

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 and updates DNS after a failover, so the application can reconnect without manual intervention. However, because the application keeps long-lived connections, it must implement connection retry or reconnect logic to detect the broken connection and re-resolve the DNS name to the new writer. This combination ensures writes resume automatically after failover.

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 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, always-running core infrastructure (e.g., a small database and application server) in the secondary Region, replicating data continuously. During a regional outage, you can rapidly scale up the environment by provisioning additional resources (e.g., EC2 instances from pre-baked AMIs) to become fully active, meeting the recovery time objective (RTO) of a few hours while keeping ongoing costs lower than a fully active second Region.

Answer

Backup and restore

Answer

Multi-site active-active

Answer

Single-AZ deployment

Question 14

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 15

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.. Option A is correct because a failover routing policy in Route 53 explicitly designates one record as primary and another as secondary, which is exactly the active-passive behavior the business wants: new clients resolve to the primary Region while it is healthy and to the secondary Region when it is not. Option B is correct because the failover policy only switches when the primary record's health is known to be failing, so a Route 53 health check must be created and associated with the primary endpoint (the primary ALB or its DNS name) to drive that automatic failover. Option C is not appropriate because weighted routing with a 50/50 split distributes traffic to both Regions simultaneously rather than keeping the secondary idle until failure. Option D is not appropriate because latency-based routing selects the fastest Region for each client and does not implement primary/secondary failover based on endpoint health. Option E is not appropriate because a geolocation policy without health checks routes by client location and cannot automatically fail over when the primary endpoint becomes unhealthy.

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 16

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 17

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 18

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 19

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 20

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.