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Design Resilient Architectures

382 questions

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Question 81Question →

A company hosts its core transactional platform on Amazon EC2 instances behind an Application Load Balancer (ALB) in us-east-1 as the primary region. The company maintains a fully functional but scaled-down warm standby environment behind an ALB in us-west-2 as the secondary region. The database layer is replicated across both regions. A solutions architect must design a DNS routing strategy using Amazon Route 53 to automatically redirect user traffic from the primary region to the secondary region if the primary region's ALB or backend instances fail. Which configuration should the solutions architect implement to meet these requirements?

Show answer & explanation

Answer: Create Route 53 Failover Alias records for the application's domain. Point the primary record to the us-east-1 ALB and the secondary record to the us-west-2 ALB, with 'Evaluate Target Health' set to Yes for both records.

Answer

Create Route 53 Failover Alias records for the application's domain. Point the primary record to the us-east-1 ALB and the secondary record to the us-west-2 ALB, with 'Evaluate Target Health' set to Yes for both records.
The correct configuration is to create Route 53 Failover Alias records pointing to the primary and secondary Application Load Balancers (ALBs) and to enable 'Evaluate Target Health'. Route 53 Failover routing is designed specifically for active-passive disaster recovery setups. By using Alias records and enabling 'Evaluate Target Health', Route 53 utilizes the health check configuration of the ALBs. If the primary ALB or all backend EC2 instances registered to it fail their health checks, Route 53 automatically detects this and redirects traffic to the secondary ALB in the warm standby region.

Step-by-Step Solution

1
Select Route 53 Failover routing policy for the domain's record set.
Defines an active-passive configuration where traffic is directed to the primary resource by default and to the secondary resource when the primary is unhealthy.
This matches the requirement to redirect traffic to the warm standby in us-west-2 only if the primary us-east-1 environment becomes unavailable.
2
Configure the primary Failover record as an Alias record pointing to the primary ALB, and the secondary Failover record as an Alias record pointing to the secondary ALB.
Allows Route 53 to map the domain name directly to the AWS ALB DNS names without incurring CNAME lookup costs or delays.
Alias records are the recommended way to integrate Route 53 with AWS load balancers.
3
Enable 'Evaluate Target Health' on both the primary and secondary Alias records.
Route 53 actively monitors the health of the underlying ALB target groups using the load balancer's configured health checks.
If target health evaluation is disabled, Route 53 will continue to route traffic to the primary ALB even if all backend instances behind it are unhealthy.

Key Concept

Route 53 Routing Policies and DNS Failover Strategies
Question 82Question →

A company hosts a web application on Amazon EC2 instances within an Auto Scaling group (ASG) behind an Application Load Balancer (ALB). The solutions architect notices that when the application on an EC2 instance crashes and returns HTTP 5xx errors, the ALB marks the instance as unhealthy, but the ASG does not terminate or replace the instance. What configuration change should the solutions architect make to ensure that the ASG automatically replaces instances that fail the application-level health checks?

Show answer & explanation

Answer: Configure the Auto Scaling group to use ELB health checks instead of EC2 health checks.

Answer

Configure the Auto Scaling group to use ELB health checks instead of EC2 health checks.
The correct action is to configure the Auto Scaling group (ASG) to use Elastic Load Balancing (ELB) health checks. By default, an ASG only monitors EC2 status checks (system and instance status). When the ELB health check type is enabled, the ASG monitors the health status of the instances in the target group. If the Application Load Balancer (ALB) marks an instance as unhealthy (e.g., due to failing application-level HTTP health checks), the ASG will automatically terminate and replace that instance, maintaining application availability.

Step-by-Step Solution

1
Analyze why the Auto Scaling group is not replacing the instances.
By default, the Auto Scaling group uses EC2 status checks (hardware and hypervisor checks), which show the instances as healthy even if the application running on them has crashed.
To fix this, the ASG must be configured to check the application health rather than just the instance status.
2
Select the appropriate health check mechanism.
The Application Load Balancer already performs application-level health checks and marks instances as unhealthy when they return 5xx errors.
By changing the ASG's health check type to ELB, the ASG will query the target group's health status and replace instances that fail ELB health checks.

Key Concept

Auto Scaling Group Health Check Configuration
Question 83Question →

A logistics company runs a fleet tracking application on AWS. The application database is hosted on Amazon RDS for PostgreSQL in a Multi-AZ deployment within the primary Region. The company requires a disaster recovery (DR) strategy in a secondary Region with a Recovery Time Objective (RTO) of 30 minutes and a Recovery Point Objective (RPO) of 15 minutes, while minimizing ongoing costs. Which architecture will meet these requirements at the lowest cost?

Show answer & explanation

Answer: Configure a cross-region Amazon RDS read replica in the secondary Region. Deploy a Pilot Light environment for the application tier in the secondary Region with Auto Scaling group capacity set to zero. Upon failover, promote the read replica to a standalone DB instance, scale up the Auto Scaling groups, and update Route 53 failover records.

Answer

Configure a cross-region Amazon RDS read replica in the secondary Region, deploy a Pilot Light environment for the application tier with Auto Scaling group capacity set to zero, and promote the replica and scale the instances during failover.
The configuration utilizing a cross-region RDS read replica satisfies the 15-minute RPO requirement because data is continuously replicated asynchronously. Using a Pilot Light strategy with Auto Scaling groups set to zero instances minimizes running compute costs during normal operations while allowing the servers to boot and scale within the 30-minute RTO during a disaster scenario.

Step-by-Step Solution

1
Set up a cross-region Amazon RDS read replica in the secondary Region.
Asynchronous replication is established, achieving an RPO of under 15 minutes.
Ensures that database changes in the primary Region are continually replicated to the recovery Region.
2
Deploy a Pilot Light environment for the application servers in the secondary Region, configuring the Auto Scaling groups with a desired capacity of zero.
Compute costs are minimized since no instances run during normal operations, but launch configurations/templates are prepared.
Allows quick provisioning of the compute layer within the 30-minute RTO window when a disaster is declared.
3
Configure a Route 53 routing policy with health checks to manage failover.
Traffic can be redirected to the secondary Region after promotion and scaling are complete.
Ensures client traffic is pointed to the promoted infrastructure in the disaster recovery Region.

Key Concept

Disaster recovery strategies involving Pilot Light environments and RDS cross-region replication to balance RTO, RPO, and cost.
Question 84Question →

A pharmaceutical company hosts a clinical trial monitoring application on AWS in the `us-east-1` Region. The application's database tier is running on an Amazon RDS for PostgreSQL Multi-AZ DB instance. The application tier runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer. The company needs to design a disaster recovery (DR) plan in the `us-west-2` Region. The DR plan must meet a Recovery Time Objective (RTO) of 33 hours and a Recovery Point Objective (RPO) of 1515 minutes. The company wants to minimize ongoing costs during normal operations. Which of the following database and application tier strategies should a solutions architect recommend to meet these requirements?

Show answer & explanation

Answer: Configure an Amazon RDS for PostgreSQL cross-region read replica in the `us-west-2` Region. Copy the application EC2 Amazon Machine Image (AMI) to the `us-west-2` Region. In the backup Region, pre-configure an Application Load Balancer and an Auto Scaling group with a minimum capacity of 00. During a failover event, promote the replica, scale up the Auto Scaling group, and update Amazon Route 53 active-passive failover routing.

Answer

The correct strategy is to configure a cross-region read replica in the backup Region, copy the application AMI, pre-configure the load balancer and an Auto Scaling group set to 00 minimum capacity, and promote/scale resources only during failover.
The correct strategy uses a Pilot Light model where database replication is active (via a cross-region RDS read replica) to satisfy the 1515-minute RPO, while the compute resources (EC2 instances in an Auto Scaling group) are kept offline (capacity set to 00) to minimize costs. Since the RTO is 33 hours, there is sufficient time to promote the replica to primary, scale up the Auto Scaling group from the copied AMI, and update Route 53 routing.

Step-by-Step Solution

1
Analyze the RTO and RPO constraints (33 hours and 1515 minutes) and the cost constraint.
The low RPO (1515 minutes) requires continuous database replication. The generous RTO (33 hours) allows the application tier to remain offline during normal operations to minimize compute costs.
This defines a Pilot Light disaster recovery model, where data is kept current but compute resources are only launched when a disaster occurs.
2
Determine the database replication strategy.
An Amazon RDS cross-region read replica provides asynchronous replication with lag typically measured in seconds, meeting the 1515-minute RPO.
Cross-region replicas are the standard mechanism to replicate RDS databases across AWS Regions for disaster recovery.
3
Determine the application tier deployment strategy to minimize operational costs.
Keeping the application instances shut down or the Auto Scaling group size at 00 in the backup Region avoids EC2 compute costs. Copying the AMI ensures that instances can be launched quickly during failover.
This meets the cost minimization requirement while ensuring the application can be restored within the 33-hour window.

Key Concept

Disaster Recovery (DR) Strategies (Pilot Light vs. Warm Standby vs. Active-Active) and RDS Cross-Region Replication
Estimated Time:2m 0s
Question 85Question →

An online auction platform allows users to submit bids on items. The platform must process these bids in the exact chronological sequence in which they are received to ensure that the correct winning bid is determined. Bidding activity is highly variable, with sudden spikes in traffic during the final minutes of popular auctions. The architecture must decouple the bid submission layer from the backend processing system to handle these traffic spikes without losing any bids. Which solution meets these requirements with the least operational overhead?

Show answer & explanation

Answer: Configure the bid submission layer to send events to an Amazon SQS FIFO queue, using the auction item ID as the message group ID. Have the backend processing system consume messages from the queue.

Answer

Configuring the bid submission layer to send events to an Amazon SQS FIFO queue, using the auction item ID as the message group ID, and having the backend processing system consume messages from the queue.
The correct solution uses an Amazon SQS FIFO queue to decouple the application components while guaranteeing that bids are processed in the exact order they are received. By using the auction item ID as the message group ID, the queue ensures that bids for the same auction item are processed sequentially, while bids for different items can be processed in parallel. This serverless approach minimizes operational overhead.

Step-by-Step Solution

1
Analyze the requirements for ordering and decoupling.
The system requires strict chronological processing (ordering) and must decouple the frontend from the backend to handle sudden traffic spikes (queuing/decoupling).
This establishes the necessary AWS services (like Amazon SQS FIFO) that support both decoupling and message ordering.
2
Evaluate Amazon SQS queue types.
Amazon SQS FIFO queues guarantee that messages are processed in the exact order they are received, whereas standard SQS queues only offer best-effort ordering.
This rules out standard SQS queues, which could process bids out of order.
3
Determine the partition/grouping strategy and operational overhead.
Using the auction item ID as the message group ID in SQS FIFO allows parallel processing across different auctions while maintaining strict ordering within each auction, with minimal operational overhead.
This ensures both ordering correctness and high performance without the overhead of managing stream shards or database polling loops.

Key Concept

Decoupling message queues with ordering guarantees (SQS FIFO)
Estimated Time:1m 30s
Question 86Question →

A logistics company is designing an application to process real-time status updates for package deliveries. The updates must be processed in the exact order they are generated for each package to ensure accurate tracking. If a status update fails to process, it must be isolated for analysis without interrupting the processing of subsequent updates for other packages. Which combination of steps will meet these requirements with the least operational overhead? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Create an Amazon SQS FIFO queue to store the delivery status updates.; Configure an Amazon SQS FIFO dead-letter queue (DLQ) to receive messages that fail to process successfully.

Answer

Create an Amazon SQS FIFO queue to store the delivery status updates, and configure an Amazon SQS FIFO dead-letter queue (DLQ) to receive messages that fail to process successfully.
To process package updates in the exact order they are generated, the architecture must use Amazon SQS FIFO queues. SQS FIFO queues guarantee first-in, first-out delivery within a message group. Additionally, isolating failed messages without blocking the queue is achieved by using a dead-letter queue (DLQ). Because the primary queue is a FIFO queue, the associated DLQ must also be a FIFO queue.

Step-by-Step Solution

1
Select a message queue service that guarantees first-in, first-out ordering.
Amazon SQS FIFO queue is chosen to ensure status updates are processed in order for each package.
Standard SQS queues cannot guarantee strict message ordering.
2
Set up a dead-letter queue (DLQ) to isolate failed messages.
An SQS FIFO queue is created and configured as the DLQ for the main SQS FIFO queue.
FIFO queues require FIFO DLQs to preserve ordering and delivery characteristics.

Key Concept

Decoupling event-driven architectures with Amazon SQS FIFO queues and FIFO dead-letter queues to guarantee order and handle processing failures.
Question 87Question →

A software-as-a-service (SaaS) company hosts a global hotel booking platform in the eu-west-1 Region. The application tier runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer. The database tier uses an Amazon RDS for PostgreSQL DB instance. The company wants to implement a disaster recovery (DR) strategy in the us-east-1 Region that achieves a recovery point objective (RPO) of 5 minutes and a recovery time objective (RTO) of 30 minutes. Which combination of actions should the solutions architect recommend to meet these requirements at the lowest cost? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Create an Amazon RDS cross-region read replica in the secondary region, and promote the replica to a standalone DB instance during a failover event.; Deploy the application infrastructure in the secondary region using AWS CloudFormation, and configure the Auto Scaling group with a desired capacity of 0.

Answer

Creating an Amazon RDS cross-region read replica and promoting it during failover, along with deploying the secondary application infrastructure using AWS CloudFormation with the Auto Scaling group's desired capacity set to 0.
The correct solution uses a Pilot Light disaster recovery strategy. Creating an Amazon RDS cross-region read replica ensures database replication with an RPO of under 5 minutes, and promoting it to a standalone database during failover satisfies the RTO of 30 minutes. Deploying the application tier using AWS CloudFormation with the Auto Scaling group's desired capacity set to 0 minimizes cost by not running any EC2 instances until a failover is needed, while still allowing the application to be launched within the 30-minute RTO.

Step-by-Step Solution

1
Analyze the RPO requirement (5 minutes) and choose the appropriate database replication mechanism.
An Amazon RDS cross-region read replica is selected, as it replicates asynchronously across regions with very low lag (usually seconds to minutes), satisfying the 5-minute RPO.
A database backup/restore method would fail the RPO, and Multi-AZ cannot span multiple regions.
2
Analyze the RTO requirement (30 minutes) and cost constraint to determine the compute tier strategy.
Choose the Pilot Light strategy by pre-staging the infrastructure with AWS CloudFormation and setting the Auto Scaling group desired capacity to 0.
This avoids running compute resources continuously (saving cost) while ensuring that the EC2 instances can be provisioned and scaled up within the 30-minute window.
3
Combine the database and compute tier actions to form the complete disaster recovery plan.
A cross-region read replica handles the database, and CloudFormation with a desired capacity of 0 handles the compute tier.
This combination satisfies both RPO and RTO requirements at the lowest cost.

Key Concept

Disaster Recovery (DR) patterns in AWS prioritize tradeoffs between RTO, RPO, and cost. A Pilot Light strategy pre-stages infrastructure (such as CloudFormation templates and scaled-down resources) and replicates database data asynchronously to meet low RPO/RTO targets while minimizing compute costs.
Estimated Time:2m 0s
Question 88Question →

An e-commerce company is designing an order processing application on AWS. When a customer places an order, the application must publish order events to multiple downstream services. The transaction service must process payments in the exact order they are received to ensure ledger accuracy. However, the shipping notification service and the analytics service can process events asynchronously without strict ordering requirements. If a service fails to process an order event after multiple retries, the event must be isolated for troubleshooting without blocking other orders.

Which TWO configurations should a solutions architect recommend to meet these requirements with the least operational overhead?

Select all that apply

Show answer & explanation

Answer: Publish order events to an Amazon SNS FIFO topic. Subscribe an Amazon SQS FIFO queue for the transaction service, and subscribe standard Amazon SQS queues for the shipping and analytics services.; Configure a redrive policy on the SQS queues to redirect failed messages to a dead-letter queue (DLQ) after the maximum receive count is exceeded.

Answer

Publishing order events to an Amazon SNS FIFO topic with SQS FIFO and standard SQS queues subscribed, combined with configuring redrive policies to a dead-letter queue (DLQ) for failed messages.
Publishing events to an Amazon SNS FIFO topic enables message fan-out to multiple downstream queues while preserving ordering. Subscribing an SQS FIFO queue ensures the transaction service processes orders sequentially, while subscribing standard SQS queues for shipping and analytics allows them to run asynchronously without ordering constraints. Using SQS redrive policies to a DLQ isolates failed messages after a specified number of retries, preventing head-of-line blocking.

Step-by-Step Solution

1
Determine the event routing and fan-out mechanism.
Amazon SNS FIFO is selected as the publisher because it supports fan-out to multiple subscribers while maintaining strict message ordering and deduplication.
The system needs to send the same order event to multiple downstream systems (transaction, shipping, analytics).
2
Select the appropriate SQS queue types for each subscriber.
An SQS FIFO queue is configured for the transaction service to guarantee ordered processing. Standard SQS queues are configured for shipping and analytics to allow asynchronous, high-throughput processing.
The transaction service requires strict chronological order, whereas shipping and analytics do not.
3
Configure error handling and message isolation.
Enable a redrive policy on the SQS queues pointing to an SQS dead-letter queue (DLQ).
Failed messages must be isolated for analysis without blocking subsequent messages in the queues.

Key Concept

Decoupling event-driven architectures using Amazon SNS FIFO fan-out to SQS queues, combined with dead-letter queues (DLQ) for fault isolation.
Estimated Time:2m 0s
Question 89Question →

A software-as-a-service (SaaS) provider is building a collaborative document editing platform. When a user updates a document, the platform must send change notifications to a real-time collaboration service and a document version history service. The updates for each individual document must be processed in the exact order they occur to prevent version conflicts. Which combination of steps should a solutions architect take to decouple these services while ensuring correct update order? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Publish the update events to an Amazon SNS FIFO topic using the document ID as the message group ID.; Create two Amazon SQS FIFO queues, subscribe them to the SNS FIFO topic, and have each backend service consume messages from its own queue.

Answer

To decouple the services while preserving ordering and enabling fan-out, publish update events to an Amazon SNS FIFO topic with a message group ID based on the document ID, and subscribe two Amazon SQS FIFO queues to the topic, with each backend service consuming from its own queue.
Publishing events to an Amazon SNS FIFO topic with a message group ID based on the document ID ensures that all updates for a specific document are ordered sequentially and delivered to subscribers in that order. Subscribing two separate Amazon SQS FIFO queues to the SNS FIFO topic allows the message to be fanned out so that both backend services receive every event, and using SQS FIFO queues ensures that the order is preserved during consumer processing.

Step-by-Step Solution

1
Identify the need for event fan-out to multiple independent backend services.
Confirm that both the real-time collaboration service and the version history service must receive every event.
This establishes that a fan-out architecture (SNS) is required.
2
Choose a messaging service that supports fan-out while preserving strict message ordering.
Select Amazon SNS FIFO as the pub/sub component.
SNS FIFO guarantees first-in, first-out delivery to its subscribers.
3
Group messages by the document ID during publication.
Updates for the same document are processed sequentially.
Using the document ID as the message group ID ensures ordering is maintained per document while allowing parallel processing across different documents.
4
Ensure each receiving service has its own dedicated queue subscribed to the SNS FIFO topic.
Two SQS FIFO queues are created and subscribed to the SNS FIFO topic.
Each service requires a separate queue to receive all events (fan-out), and using SQS FIFO queues preserves the ordering guaranteed by the SNS FIFO topic.

Key Concept

End-to-end FIFO ordering in a fan-out architecture using SNS FIFO and SQS FIFO.
Question 90Question →

A smart home automation company processes real-time state change events, such as lock and unlock actions, from millions of smart door locks globally. For security auditing compliance, the events from each individual lock must be processed in the exact sequence they are generated. During peak hours, the backend database experiences write throttling due to sudden spikes in traffic. A solutions architect needs to decouple the ingestion and processing layers to handle the spikes while guaranteeing lock-level event ordering. Which combination of actions should the solutions architect recommend to meet these requirements? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Create an Amazon SNS FIFO topic to receive the lock events, and subscribe an Amazon SQS FIFO queue to the topic.; Configure the event generator to use the unique lock ID as the Message Group ID when publishing events to the SNS FIFO topic.

Answer

To decouple the ingestion and processing layers while preserving ordering, the solutions architect must use an Amazon SNS FIFO topic to receive the events and subscribe an Amazon SQS FIFO queue to it, while setting the Message Group ID to the unique lock ID.
To meet compliance requirements, events must be processed in the exact order they occurred. Creating an Amazon SNS FIFO topic and subscribing an Amazon SQS FIFO queue provides a decoupled, resilient architecture that guarantees ordered message delivery. By utilizing the unique lock ID as the Message Group ID, the system ensures that messages for a specific lock are serialized and processed in order, while multiple consumers can still process events for different locks concurrently.

Step-by-Step Solution

1
Establish an ingestion and queuing system that supports ordering.
Use Amazon SNS FIFO topics and Amazon SQS FIFO queues to decouple messaging.
FIFO services guarantee that messages are delivered in the exact order they are received, preventing out-of-order processing.
2
Configure ordering granularity per lock ID.
Use the unique lock ID as the Message Group ID when publishing events.
The Message Group ID specifies that all messages belonging to the same group (lock ID) must be processed sequentially, while allowing parallel processing for different locks to ensure high throughput.

Key Concept

Decoupled architecture using SNS FIFO and SQS FIFO with Message Group IDs to preserve ordering per logical entity.
Estimated Time:1m 30s
Question 91Question →

A company wants to set up an active-passive disaster recovery (DR) strategy for its primary web application running on an Application Load Balancer in the us-east-1 Region. The backup environment is a static maintenance page hosted in an Amazon S3 bucket in the us-west-2 Region. Which Amazon Route 53 configuration will meet this requirement with the least administrative effort during a failover event?

Show answer & explanation

Answer: Configure an Amazon Route 53 Failover routing policy, designating the Application Load Balancer as the primary record associated with an active health check, and the S3 bucket as the secondary record.

Answer

Configure an Amazon Route 53 Failover routing policy, designating the Application Load Balancer as the primary record associated with an active health check, and the S3 bucket as the secondary record.
The correct configuration uses a Route 53 Failover routing policy. In this setup, the primary record points to the active application endpoint (the Application Load Balancer) and is associated with a health check. The secondary record points to the disaster recovery resource (the S3 bucket hosting the static page). Route 53 continuously monitors the health of the primary endpoint and automatically shifts traffic to the secondary endpoint if the primary endpoint fails the health check, requiring no manual intervention.

Step-by-Step Solution

1
Identify the primary active resource and the secondary passive resource.
The Application Load Balancer is the primary active endpoint, and the S3 bucket is the secondary passive endpoint.
Active-passive disaster recovery requires establishing a clear primary path for regular traffic and a secondary path for failover situations.
2
Select the Route 53 routing policy designed for active-passive recovery.
Select the Failover routing policy.
Failover routing is built specifically to redirect traffic when a primary resource becomes unhealthy.
3
Associate an active health check with the primary record.
Route 53 will monitor the health of the Application Load Balancer and fail over to the S3 bucket if the health check fails.
Without a health check on the primary record, Route 53 cannot determine whether the primary endpoint is healthy and will not trigger the failover.

Key Concept

Route 53 Failover routing policy allows solutions architects to implement active-passive disaster recovery configurations by directing traffic to a secondary resource when the primary resource's health check fails.
Question 92Question →

An e-commerce company is migrating its ordering database to AWS and requires a resilient design using Amazon RDS for PostgreSQL. The database must survive an Availability Zone (AZ) outage with a Recovery Time Objective (RTO) of under 60 seconds, and it must support horizontal read scaling for search queries within the same AWS Region. Which configuration meets these requirements with the lowest operational overhead?

Show answer & explanation

Answer: Deploy a Multi-AZ DB cluster with one primary and two readable standby DB instances.

Answer

Deploy a Multi-AZ DB cluster with one primary and two readable standby DB instances.
The correct configuration is a Multi-AZ DB cluster with one primary and two readable standby DB instances. This option provides high availability by automatically failing over in less than 35 seconds, which satisfies the RTO requirement. It also natively supports horizontal read scaling because both standby DB instances can accept read requests through the reader endpoint.

Step-by-Step Solution

1
Analyze high availability and read scaling requirements.
The configuration must support a failover time (RTO) of less than 60 seconds during an Availability Zone outage and offer read scalability within the same region.
This establishes the constraints needed to rule out configurations that do not support automated failover or read endpoint integration.
2
Compare Multi-AZ DB instances against Multi-AZ DB clusters.
A standard Multi-AZ DB instance provides failover but the standby instance cannot serve read traffic. A Multi-AZ DB cluster provides automated failover and allows its two standby instances to process read queries.
Choosing the cluster configuration satisfies both failover and read scaling within a single native RDS architecture, minimizing operational complexity.
3
Verify compliance with the RTO constraint.
Amazon RDS Multi-AZ DB clusters fail over in under 35 seconds, which is well within the 60-second RTO.
This confirms the proposed architecture meets all defined service level requirements.

Key Concept

Amazon RDS Multi-AZ DB clusters combine high availability (automated failover) and read scalability by deploying a primary and two readable standby instances across three Availability Zones.
Estimated Time:2m 0s
Question 93Question →

An enterprise is deploying an active-passive disaster recovery (DR) architecture for a stateful web application. The primary environment is in us-west-2 with an Application Load Balancer (ALB) and an Amazon Aurora PostgreSQL database. The secondary environment in us-east-1 is a warm standby with a scaled-down Amazon EC2 fleet behind another ALB, and an Aurora read replica. The DR plan requires Route 53 to automatically shift DNS traffic to us-east-1 only if the primary ALB has no healthy EC2 targets, or if the primary application cannot connect to its database (determined by the absence of the string 'DB_OK' on the '/healthz' status page). The database promotion to primary will be handled by a separate automated script. Which Route 53 DNS failover configuration meets these requirements with the shortest recovery time?

Show answer & explanation

Answer: Configure a Route 53 HTTP health check that queries the us-west-2 ALB DNS name at /healthz and checks for the string DB_OK. Create a primary Failover Alias record pointing to the us-west-2 ALB, set Evaluate Target Health to Yes, and associate it with the Route 53 health check. Create a secondary Failover Alias record pointing to the us-east-1 ALB with Evaluate Target Health set to Yes.

Answer

Configure a Route 53 HTTP health check that queries the us-west-2 ALB DNS name at /healthz and checks for the string DB_OK. Create a primary Failover Alias record pointing to the us-west-2 ALB, set Evaluate Target Health to Yes, and associate it with the Route 53 health check. Create a secondary Failover Alias record pointing to the us-east-1 ALB with Evaluate Target Health set to Yes.
The correct configuration uses Route 53 Failover Alias records combined with both Route 53 health checks and the Evaluate Target Health feature. Evaluate Target Health allows Route 53 to monitor the backend EC2 targets of the Application Load Balancer (ALB). Associating the Route 53 health check that performs response body string matching for 'DB_OK' ensures that deep application failures (such as database connectivity issues) are also detected. If either the ALB targets fail or the health check fails to find the string, Route 53 automatically fails over to the standby region.

Step-by-Step Solution

1
Configure the application-level health check
A Route 53 HTTP health check is created to target the primary ALB DNS endpoint at /healthz, configured to fail if the response body does not contain the string DB_OK.
The Application Load Balancer cannot inspect the response body for specific strings on its own; hence, a Route 53 external health check is required to verify deep database connectivity.
2
Configure the Route 53 primary Failover Alias record
A primary Failover Alias record is created pointing to the us-west-2 ALB, with Evaluate Target Health set to Yes and associated with the health check created in Step 1.
Enabling Evaluate Target Health ensures Route 53 monitors target group health (infrastructure level), while associating the Route 53 health check ensures application-level status is evaluated. If either fails, the record is marked unhealthy.
3
Configure the Route 53 secondary Failover Alias record
A secondary Failover Alias record is created pointing to the us-east-1 ALB, with Evaluate Target Health set to Yes.
This guarantees that if the primary region is unhealthy, Route 53 redirects DNS queries to the standby region's ALB, while keeping the standby inactive during normal operations.

Key Concept

Route 53 Active-Passive Failover with Alias Records and Target Health Evaluation
Question 94Question →

A company's enterprise application runs on AWS and uses an Amazon RDS for SQL Server database to store transactional data. The database must be designed to withstand an Availability Zone outage in the primary AWS Region with automatic failover to minimize downtime. Furthermore, the company requires a disaster recovery strategy to support recovery in a secondary AWS Region with a Recovery Point Objective (RPO) of less than 30 minutes.

Which two database configurations should the solutions architect select to meet these requirements? (Select two.)

Select all that apply

Show answer & explanation

Answer: Configure the RDS for SQL Server database with a Multi-AZ deployment.; Create a cross-region read replica of the RDS for SQL Server database in the secondary AWS Region.

Answer

The correct configurations are configuring the database with a Multi-AZ deployment and creating a cross-region read replica in the secondary region.
The correct options are configuring the RDS database as a Multi-AZ deployment and creating a cross-region read replica. Multi-AZ replication is synchronous and provides automatic failover within the primary region, securing high availability. A cross-region read replica replicates data asynchronously to the secondary region, keeping the recovery point well within the 30-minute requirement and offering a promotable primary target for disaster recovery.

Step-by-Step Solution

1
Analyze high availability requirements in the primary region
Determine that a Multi-AZ deployment is required for synchronous replication and automatic failover.
Multi-AZ provides automated failover to minimize downtime during Availability Zone outages without manual intervention.
2
Analyze disaster recovery requirements in the secondary region
Determine that a cross-region read replica is required to meet the 30-minute RPO.
Cross-region read replicas use continuous asynchronous replication to keep data updated in near-real-time in the secondary region.

Key Concept

Multi-AZ and Cross-Region replication configurations for relational database resilience.
Question 95Question →

A media streaming company hosts its user profile database in the us-east-1 Region. The application requires local, sub-second read performance for users in the eu-west-1 Region. Additionally, the architecture must support a cross-region disaster recovery strategy with a Recovery Point Objective (RPO) of less than 55 seconds and a Recovery Time Objective (RTO) of less than 55 minutes. Which database configuration meets these requirements with the least operational overhead?

Show answer & explanation

Answer: Configure an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in eu-west-1.

Answer

Configure an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in eu-west-1.
The correct database configuration is an Amazon Aurora Global Database with the primary cluster in us-east-1 and a secondary cluster in eu-west-1. Aurora Global Database uses dedicated storage-based replication that delivers sub-second replication latency (typically under 11 second), meeting the 55-second RPO. In the event of a regional outage, the secondary cluster can be promoted to primary in less than 11 minute, satisfying the 55-minute RTO. This provides local reads in the secondary region with the lowest operational overhead.

Step-by-Step Solution

1
Analyze the read latency and location constraints.
The solution requires low-latency read replication from us-east-1 to eu-west-1.
This narrows the choice to configurations supporting cross-region replication.
2
Evaluate the RPO and RTO disaster recovery requirements against replication options.
Amazon Aurora Global Database supports storage-level, dedicated replication with typical lag of less than 11 second (meeting the 55-second RPO limit) and secondary cluster promotion in less than 11 minute (meeting the 55-minute RTO limit).
Standard RDS replicas and backup-based approaches cannot meet these tight recovery metrics with low operational overhead.

Key Concept

High availability and disaster recovery configurations in Amazon Aurora
Estimated Time:1m 30s
Question 96Question →

A company is designing a high-availability, active-active web application deployed across two AWS Regions: us-east-1 and eu-west-1. The application is accessed via the domain apex (example.com). The architecture requires low-latency access for global users by directing them to the nearest healthy region. Additionally, the system must support automatic failover to the secondary region if either the load balancer target servers become unhealthy or the local application instance loses connectivity to its database. Which two configurations should the solutions architect implement to meet these requirements?

Select all that apply

Show answer & explanation

Answer: Create Route 53 Latency Alias records for example.com pointing to the Application Load Balancer (ALB) in each region, and enable the Evaluate Target Health option.; Create Route 53 HTTPS health checks to monitor the application's database connectivity endpoint in each region, and associate these health checks with their corresponding Latency Alias records.

Answer

Creating Route 53 Latency Alias records pointing to the Application Load Balancers with target health evaluation enabled, and configuring custom Route 53 HTTPS health checks to monitor the database connectivity endpoint.
The correct solution requires configuring Route 53 Latency Alias records pointing to the Application Load Balancer in each region and setting 'Evaluate Target Health' to Yes. This allows traffic to be routed to the closest healthy region at the zone apex. Additionally, to detect database connectivity failures, custom Route 53 HTTPS health checks must be created to query the database connectivity endpoint and associated with the Latency Alias records.

Step-by-Step Solution

1
Address the requirement for zone apex routing and active-active low-latency routing.
Determine that Route 53 Latency Alias records pointing to the ALBs in each region must be used, as CNAME records cannot reside at the zone apex.
Alias records map the zone apex directly to AWS resources like ALBs and support Route 53's active health monitoring.
2
Configure automatic load balancer health evaluation.
Enable the 'Evaluate Target Health' option on the Latency Alias records.
This permits Route 53 to check the health of the ALB targets and stop routing traffic to a region if its web servers fail.
3
Address the requirement to monitor backend database connectivity and handle regional degradation.
Create custom HTTP/HTTPS Route 53 health checks probing a health endpoint that verifies database connectivity, and associate these health checks with the Latency Alias records.
ALB Target Group checks might not capture deep backend dependency failures, so custom health checks are required for end-to-end failover.

Key Concept

Combining Route 53 Latency Routing, Alias Records, and Multi-layered Health Checks for Active-Active Failover at the Zone Apex
Question 97Question →

A real estate platform runs its production workload in the eu-west-1 Region. The architecture consists of Amazon EC2 instances in an Auto Scaling Group behind an Application Load Balancer, and an Amazon RDS for MySQL database. The company needs to design a disaster recovery (DR) strategy in the eu-central-1 Region with a Recovery Point Objective (RPO) of 15 minutes and a Recovery Time Objective (RTO) of 4 hours. Which strategy should a Solutions Architect recommend to meet these requirements with the lowest operational cost?

Show answer & explanation

Answer: Create an RDS Cross-Region Read Replica in the secondary region. Copy EC2 AMIs and launch templates to the secondary region, and configure an Auto Scaling Group with a desired capacity of 0. During a disaster, promote the replica to a standalone database, scale up the Auto Scaling Group, and update Route 53 DNS records.

Answer

Create an RDS Cross-Region Read Replica in the secondary region, copy EC2 AMIs and launch templates, configure an Auto Scaling Group with a desired capacity of 0, and promote the database replica and scale up the Auto Scaling Group during failover.
The correct strategy uses an RDS Cross-Region Read Replica to continuously copy database changes, which meets the 15-minute RPO requirement. By maintaining the EC2 Auto Scaling Group at a capacity of 0 in the secondary region, the company avoids running compute instances during normal operations, minimizing costs. The replication promotion and Auto Scaling Group scaling processes can be completed well within the 4-hour RTO.

Step-by-Step Solution

1
Evaluate the recovery time objective (RTO) and recovery point objective (RPO) requirements.
RPO is 15 minutes, which requires active replication of data to the secondary region. RTO is 4 hours, which allows for some manual or scripted steps to provision resources during failover.
Determining the bounds of RPO and RTO guides the selection of the DR strategy (e.g., Pilot Light vs. Warm Standby vs. Backup and Restore).
2
Select the database replication method.
An RDS Cross-Region Read Replica provides asynchronous replication, ensuring replica lag is minimal (usually seconds or minutes) and meets the 15-minute RPO.
Standard backups copied to the secondary region or S3 Glacier cannot reliably guarantee a 15-minute RPO and would violate the RTO due to retrieval delays.
3
Design the compute replication strategy to minimize costs.
Store EC2 AMIs and launch templates in the secondary region, and configure an Auto Scaling Group with a desired capacity of 0. Scale it up only during failover.
Keeping EC2 instances at 0 capacity avoids ongoing compute charges, aligning with the constraint to minimize costs while easily launching instances within the 4-hour RTO window.

Key Concept

Selecting the most cost-effective disaster recovery strategy (such as Pilot Light) that satisfies recovery time (RTO) and recovery point (RPO) constraints using cross-region database replication and on-demand compute scaling.
Question 98Question →

A medical laboratory runs an automated pipeline to analyze clinical trial results. When a new trial dataset is uploaded to an Amazon S3 bucket, it must trigger two separate processes: a statistical analysis engine and a regulatory compliance auditing service. The systems must process these datasets asynchronously. If either downstream service encounters an error or fails to process a dataset, the dataset event must be isolated for analysis without disrupting the rest of the queue. The order in which datasets are processed is not critical, but each service must process a copy of every dataset event.

Which combination of steps should a solutions architect recommend to design a decoupled and resilient architecture for this application? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Configure the Amazon S3 bucket to send event notifications to an Amazon SNS topic, and subscribe two Amazon SQS standard queues to the topic, with each queue dedicated to one of the processing services.; Configure an Amazon SQS dead-letter queue (DLQ) for each of the processing queues to capture and isolate messages that cannot be processed successfully.

Answer

To build a decoupled and resilient architecture, configure Amazon S3 to publish event notifications to an Amazon SNS topic. Subscribe two separate Amazon SQS standard queues to the SNS topic, allowing each downstream service to consume a dedicated copy of the events. To handle failures gracefully, configure a dead-letter queue (DLQ) for each SQS queue to capture and isolate messages that fail to process.
To decouple the services while ensuring both the statistical analysis engine and the regulatory compliance auditing service receive a copy of every event, a fan-out pattern is required. Configuring the Amazon S3 bucket to publish to an Amazon SNS topic, and then subscribing a dedicated SQS queue for each service, satisfies this requirement. Since ordering is not critical, standard SQS queues are appropriate. To ensure resilience, attaching a Dead-Letter Queue (DLQ) to each processing SQS queue isolates messages that fail to process, preventing blocking errors in the main pipeline.

Step-by-Step Solution

1
Select a message distribution pattern that allows a single S3 event to be copied and delivered to multiple independent processing systems (fan-out pattern).
Amazon SNS is identified as the publisher, and Amazon SQS queues are identified as subscribers.
Amazon SNS supports fan-out messaging to multiple SQS queues, preventing competing consumers issues.
2
Ensure that processing failures do not block the entire message processing pipeline.
Each SQS queue is configured with a dead-letter queue (DLQ).
Failed events are diverted to the DLQ after a specific number of retries, leaving the main queue clear for subsequent datasets.

Key Concept

Decoupling multi-consumer systems using Amazon SNS and SQS fan-out with Dead-Letter Queues (DLQs) for resilient asynchronous processing.
Question 99Question →

A financial services company hosts an invoice processing platform in the us-west-2 Region. The application architecture consists of Amazon EC2 instances behind an Application Load Balancer (ALB), an Amazon RDS for PostgreSQL database for invoice metadata, and an Amazon S3 bucket for storing scanned invoice documents. The company needs to design a disaster recovery (DR) solution in the us-east-1 Region. The solution must support a Recovery Point Objective (RPO) of 15 minutes and a Recovery Time Objective (RTO) of 2 hours while keeping ongoing standby costs as low as possible. Which combination of database and storage configurations will meet these requirements? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Configure Amazon S3 Cross-Region Replication (CRR) to asynchronously copy invoice documents from the us-west-2 bucket to a destination bucket in us-east-1.; Create an Amazon RDS for PostgreSQL cross-region read replica in us-east-1 to serve as the standby database.

Answer

Configure Amazon S3 Cross-Region Replication (CRR) to asynchronously copy invoice documents from the us-west-2 bucket to a destination bucket in us-east-1, and create an Amazon RDS for PostgreSQL cross-region read replica in us-east-1 to serve as the standby database.
To meet a 15-minute RPO and a 2-hour RTO cost-effectively, a Pilot Light DR pattern is appropriate. The correct configurations include using Amazon S3 Cross-Region Replication (CRR) to copy scanned invoices from us-west-2 to us-east-1, ensuring that newly uploaded documents are replicated asynchronously within minutes. For the database tier, creating an Amazon RDS for PostgreSQL cross-region read replica ensures the metadata is continuously replicated asynchronously with low lag (satisfying the 15-minute RPO) and can be promoted to primary status within minutes during a failover event (satisfying the 2-hour RTO).

Step-by-Step Solution

1
Analyze the storage replication requirements for the RPO of 15 minutes.
Identify that Amazon S3 Cross-Region Replication (CRR) provides automated, asynchronous replication of new objects to another region, satisfying the RPO for the document storage.
S3 Lifecycle rules alone cannot copy data across regions directly into S3 Glacier without replication, and Glacier retrieval times would violate the RTO.
2
Analyze the database replication requirements for the RPO of 15 minutes and RTO of 2 hours.
Determine that an Amazon RDS for PostgreSQL cross-region read replica keeps the standby database updated asynchronously with minimal lag, satisfying the 15-minute RPO, and can be promoted to a standalone primary database quickly, satisfying the 2-hour RTO.
Daily database snapshots via AWS Backup only guarantee a 24-hour RPO and require a lengthy restore process, which violates the 15-minute RPO and 2-hour RTO requirements.
3
Evaluate the routing and failover automation options.
Discard options attempting to use Route 53 latency routing to automate RDS promotion, as Route 53 is a DNS service and cannot perform database-level operations or promote read replicas.
RDS read replicas require explicit promotion to become writeable, and Route 53 does not manage database failover.

Key Concept

Designing a pilot light multi-region disaster recovery architecture utilizing Amazon S3 Cross-Region Replication and Amazon RDS cross-region read replicas to meet stringent RTO and RPO constraints cost-effectively.
Estimated Time:2m 0s
Question 100Question →

A collaborative online whiteboard platform runs its production environment in the us-east-1 Region. The architecture includes an Application Load Balancer, an Auto Scaling group of Amazon EC2 instances, and an Amazon RDS for PostgreSQL database. The company needs to design a disaster recovery (DR) plan in the us-west-2 Region. The design must meet a Recovery Time Objective (RTO) of 4 hours and a Recovery Point Objective (RPO) of 15 minutes while minimizing ongoing infrastructure costs.

Which strategy should a solutions architect recommend to meet these requirements?

Show answer & explanation

Answer: Establish a pilot light recovery strategy by creating an Amazon RDS cross-region read replica in the secondary Region, and using AWS CloudFormation templates to deploy the Application Load Balancer and Auto Scaling group only when a failover is initiated.

Answer

Establish a pilot light recovery strategy by creating an Amazon RDS cross-region read replica in the secondary Region, and using AWS CloudFormation templates to deploy the Application Load Balancer and Auto Scaling group only when a failover is initiated.
The pilot light strategy is the most cost-effective option that meets the RTO of 4 hours and RPO of 15 minutes. An Amazon RDS cross-region read replica provides asynchronous replication with lag typically measured in seconds, satisfying the 15-minute RPO. Since the RTO is 4 hours, there is sufficient time to use AWS CloudFormation to provision the Application Load Balancer and the Auto Scaling group of EC2 instances when a disaster is declared, avoiding the ongoing compute costs of a warm standby.

Step-by-Step Solution

1
Analyze the RTO and RPO requirements.
The RTO is 4 hours, which allows sufficient time to deploy compute resources on demand. The RPO is 15 minutes, which requires continuous database replication rather than daily backup copies.
This establishes the technical constraints for computing (dynamic deployment is allowed) and data (replication must be near real-time).
2
Evaluate the cost constraint.
To minimize ongoing infrastructure costs, the standby region should run as few active compute resources as possible during normal operations.
Running compute instances (like in a warm standby or active-active setup) increases ongoing costs, which must be avoided.
3
Select the optimal disaster recovery pattern.
A pilot light pattern keeps the database replicated live using a cross-region read replica, but leaves the application and load balancing tiers unprovisioned until failover, using CloudFormation to build them when needed.
This meets both the 15-minute RPO and 4-hour RTO while achieving the lowest possible idle infrastructure costs.

Key Concept

Disaster recovery strategies differ in RTO, RPO, and cost; pilot light minimizes costs by only keeping data replication active and provisioning compute resources on demand.
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