SAA-C03 Design Resilient Architectures — Timed 10 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.