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Design Resilient Architectures

382 questions

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Question 361Question →

A real estate platform allows agents to update property listing details. When a listing is updated, the platform must concurrently update the search index, regenerate watermarked images of the property, and send email alerts to prospective buyers. To prevent older data from overwriting newer updates, changes to each property listing must be processed in the exact chronological order they were submitted. The image watermarking and email alert processes do not require strict ordering but must be decoupled to handle traffic spikes.

Which solution meets these requirements with the least operational overhead?

Show answer & explanation

Answer: Publish listing update events to an Amazon SNS FIFO topic. Subscribe three Amazon SQS FIFO queues to the SNS FIFO topic, with each queue feeding one of the downstream services: search indexing, image watermarking, and email alerts.

Answer

Publish listing update events to an Amazon SNS FIFO topic. Subscribe three Amazon SQS FIFO queues to the SNS FIFO topic, with each queue feeding one of the downstream services: search indexing, image watermarking, and email alerts.
The correct solution uses an Amazon SNS FIFO topic to fan out events to three separate Amazon SQS FIFO queues. This pattern ensures that each downstream service (search indexing, image watermarking, and email alerts) receives its own copy of the listing update event (fan-out) and processes them in the exact order they were published (FIFO), preventing race conditions where older updates could overwrite newer listing data.

Step-by-Step Solution

1
Analyze the concurrency and ordering requirements.
The platform needs to distribute listing updates to three downstream services (fan-out) while maintaining the chronological sequence of updates per property listing (ordering).
This determines that standard publish-subscribe messaging is insufficient because it does not guarantee first-in, first-out (FIFO) delivery, which is required to prevent older updates from overwriting newer ones.
2
Determine the appropriate AWS messaging integration pattern.
To implement fan-out with strict ordering, the solution must pair Amazon SNS FIFO with Amazon SQS FIFO.
An SNS FIFO topic preserves the order of messages published to it and delivers them to subscribed SQS FIFO queues in that same order. Each service needs its own SQS FIFO queue to avoid destructive reads.
3
Evaluate the subscription configuration constraints.
Subscribing SQS FIFO queues to an SNS FIFO topic ensures message ordering is preserved from end to end.
If standard SNS or standard SQS is introduced anywhere in the pipeline, ordering guarantees are lost, and subscribing a single queue to multiple consumers would prevent all services from receiving every update.

Key Concept

End-to-end first-in, first-out (FIFO) ordering in a fan-out architecture using Amazon SNS FIFO and Amazon SQS FIFO.
Estimated Time:1m 30s
Question 362Question →

A property management portal hosts its application in the us-east-1 Region. The database tier runs on an Amazon RDS for PostgreSQL Multi-AZ DB instance. The application tier consists of Amazon EC2 instances inside an Auto Scaling group behind an Application Load Balancer. The company needs to design a disaster recovery (DR) strategy in the us-west-2 Region with a Recovery Time Objective (RTO) of 2 hours and a Recovery Point Objective (RPO) of 15 minutes. The solution must minimize ongoing operational and infrastructure costs. Which disaster recovery strategy should a solutions architect recommend to meet these requirements?

Show answer & explanation

Answer: Configure a cross-region RDS read replica in the DR region. Save the application server configurations as an Amazon Machine Image (AMI) and store the network infrastructure configurations as an AWS CloudFormation template. During a disaster, deploy the infrastructure from the template, promote the RDS read replica to a standalone database, and scale the application tier.

Answer

Configure a cross-region RDS read replica in the DR region. Save the application server configurations as an Amazon Machine Image (AMI) and store the network infrastructure configurations as an AWS CloudFormation template. During a disaster, deploy the infrastructure from the template, promote the RDS read replica to a standalone database, and scale the application tier.
The correct strategy is the Pilot Light pattern. By maintaining a cross-region RDS read replica, the database replication is continuous, satisfying the 15-minute RPO. Storing compute and networking tier configurations as CloudFormation templates and AMIs ensures that no EC2 instances or load balancers are running during normal operations, minimizing ongoing costs. Recreating these resources and promoting the RDS read replica during a failover can easily be completed within the 2-hour RTO.

Step-by-Step Solution

1
Analyze the RPO requirement of 15 minutes.
Identify that data must be replicated to the recovery region in near real-time. A cross-region Amazon RDS read replica meets this requirement by replicating data asynchronously with replication lag typically measured in seconds.
To ensure that data loss does not exceed 15 minutes in the event of a disaster.
2
Analyze the RTO requirement of 2 hours and the cost-optimization constraint.
Determine that a Pilot Light strategy is the most cost-effective approach. Instead of keeping active compute resources running, store configurations as AMIs and AWS CloudFormation templates. The 2-hour RTO allows sufficient time to deploy these templates and provision the compute tier dynamically.
To minimize running infrastructure costs in the recovery region while still meeting the recovery time limit.
3
Formulate the failover process.
During a disaster, promote the cross-region read replica to a standalone primary database, run the CloudFormation template to deploy the Application Load Balancer and Auto Scaling group, and launch instances using the saved AMIs.
To complete the recovery process and restore full service in the secondary region.

Key Concept

Disaster recovery strategies differ in RTO, RPO, and cost. A Pilot Light strategy keeps the database replication active but compute resources offline, making it highly cost-effective while still meeting moderate recovery time objectives.
Question 363Question →

A company is designing a web-based educational testing platform. When a student submits an exam, the platform must process the submission asynchronously to calculate the score, generate a PDF certificate, and send an email notification. The grading service must process the answers in the exact order they were submitted by the student to prevent concurrency issues, and multiple backend microservices must receive the submission events independently. Which solution meets these requirements with the least operational overhead?

Show answer & explanation

Answer: Publish the exam submission events to an Amazon SNS FIFO topic. Subscribe separate Amazon SQS FIFO queues for the grading, certificate, and notification services to the SNS FIFO topic.

Answer

Publish the exam submission events to an Amazon SNS FIFO topic. Subscribe separate Amazon SQS FIFO queues for the grading, certificate, and notification services to the SNS FIFO topic.
The correct solution uses an Amazon SNS FIFO topic subscribed to by multiple Amazon SQS FIFO queues. An SNS FIFO topic ensures that message ordering is preserved during fan-out, and SQS FIFO queues guarantee that the consumer microservices process the messages in the exact order they were published. This satisfies both the decoupling/fan-out requirement and the strict message ordering constraint with minimal operational overhead.

Step-by-Step Solution

1
Identify the fan-out requirement where multiple distinct services (grading, certificate, and notification) need to process the same exam submission event.
Amazon SNS is the standard AWS service to achieve event fan-out to multiple subscribers.
It allows a single published message to be delivered to multiple downstream endpoints automatically.
2
Analyze the ordering requirement which specifies that events must be processed in the exact order they are received to prevent concurrency issues.
Both the message delivery (SNS) and queueing (SQS) layers must support First-In-First-Out (FIFO) ordering.
Standard SNS and SQS queues only provide best-effort ordering, which can result in out-of-order execution.
3
Select the integration pattern that natively supports both fan-out and ordered delivery with minimal operational overhead.
Combine Amazon SNS FIFO with Amazon SQS FIFO queues.
SNS FIFO topics can deliver messages to SQS FIFO queues while preserving the message order and message group ID, eliminating the need for custom ordering or filtering logic in application code.

Key Concept

Decoupling event-driven architectures with ordering guarantees using SNS FIFO and SQS FIFO fan-out pattern.
Estimated Time:1m 30s
Question 364Question →

A retail banking compliance platform hosts its transaction reporting application in the us-east-1 Region. The application runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer, and it uses an Amazon RDS for PostgreSQL Multi-AZ DB instance. The bank wants to establish a disaster recovery (DR) strategy in the us-west-2 Region. The solution must support a Recovery Point Objective (RPO) of 10 minutes and a Recovery Time Objective (RTO) of 15 minutes, while minimizing ongoing running costs. Which solution meets these requirements?

Show answer & explanation

Answer: Create a cross-Region Read Replica of the RDS DB instance in the us-west-2 Region. Deploy a replica Application Load Balancer and a scaled-down Auto Scaling group with a minimum capacity of 1 in the us-west-2 Region. Configure Route 53 failover routing to point to the active Application Load Balancer, and promote the read replica to a standalone DB instance during failover.

Answer

Create a cross-Region Read Replica of the RDS DB instance in the us-west-2 Region. Deploy a replica Application Load Balancer and a scaled-down Auto Scaling group with a minimum capacity of 1 in the us-west-2 Region. Configure Route 53 failover routing to point to the active Application Load Balancer, and promote the read replica to a standalone DB instance during failover.
The correct strategy is a Warm Standby. To meet the 10-minute RPO, a cross-Region Read Replica is deployed in the us-west-2 Region to continuously replicate data asynchronously. To meet the 15-minute RTO, a replica Application Load Balancer and a scaled-down Auto Scaling group with a minimum capacity of 1 are deployed in the target Region. This ensures that the application is running and can immediately begin accepting traffic when Route 53 failover routing is triggered, while the Auto Scaling group scales up dynamically. During failover, the read replica is promoted to a standalone primary database instance.

Step-by-Step Solution

1
Determine the database replication strategy to satisfy the 10-minute Recovery Point Objective (RPO).
Identify that a cross-Region Read Replica replicates transactions asynchronously with minimal lag (seconds or minutes), which successfully satisfies the 10-minute RPO. Daily backups fail this requirement.
Choosing the correct replication technology is necessary to ensure data loss is kept under the target threshold.
2
Select the appropriate disaster recovery (DR) strategy to satisfy the 15-minute Recovery Time Objective (RTO).
Determine that a Warm Standby strategy (keeping a minimum capacity of 1 running instance in the target Region) is required to meet the 15-minute RTO. A Pilot Light strategy (minimum capacity of 0) takes too long to spin up, configure, and pass load balancer health checks from scratch.
Active but scaled-down services ensure immediate traffic ingestion, which minimizes failover delay.
3
Configure the failover mechanism for DNS routing.
Use Amazon Route 53 with failover routing policies pointing to the primary and secondary Application Load Balancers.
This guarantees that incoming traffic is automatically or manually redirected to the disaster recovery Region during an outage.

Key Concept

Disaster recovery strategy trade-offs (RTO and RPO) and AWS cross-region replication configurations.
Estimated Time:2m 0s
Question 365Question →

A media streaming company is building a real-time multiplayer gaming platform. The system must process player movement and action events in the exact chronological order they are received to maintain game state consistency. Additionally, the system must broadcast these events to a live leaderboard service and a security auditing service. Which combination of actions should a solutions architect recommend to meet these requirements? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Create an Amazon SNS FIFO topic and publish the game events to it.; Create Amazon SQS FIFO queues, subscribe them to the SNS FIFO topic, and configure the downstream services to consume messages from these queues.

Answer

Create an Amazon SNS FIFO topic to receive the game events, and create Amazon SQS FIFO queues subscribed to the topic for downstream services to consume.
To achieve ordered processing and fan-out, the architecture must combine an Amazon SNS FIFO topic and Amazon SQS FIFO queues. An SNS FIFO topic ensures that message ordering is maintained when fanning out to multiple subscribers. Subscribing SQS FIFO queues to this topic ensures that downstream services consume the events in the exact chronological sequence they were published.

Step-by-Step Solution

1
Analyze the ordering and fan-out requirements.
Identified that game events must be processed in strict chronological order and distributed to multiple downstream services (leaderboard and auditing).
This establishes that a FIFO (First-In-First-Out) messaging mechanism is required alongside a pub/sub fan-out pattern.
2
Select the appropriate pub/sub service.
Choose Amazon SNS FIFO topics to enable ordered fan-out.
Standard SNS topics do not guarantee message ordering, whereas SNS FIFO topics maintain the sequence of messages for all subscribed queues.
3
Select the appropriate queue type for the subscribers.
Choose Amazon SQS FIFO queues as subscribers to the SNS FIFO topic.
SNS FIFO topics only support SQS FIFO queues as subscribers, which ensures that the strict message order is preserved end-to-end for downstream consumers.

Key Concept

Decoupling with SNS FIFO and SQS FIFO for ordered fan-out architectures.
Question 366Question →

A retail company is designing an event-driven system to process stock level updates from its physical stores. The updates must be processed in the exact order they occur for each product SKU to prevent database write conflicts and maintain accurate inventory levels. The system must also be able to scale and absorb sudden spikes in update traffic during promotional sales events.

Which solution meets these requirements with the least operational overhead?

Show answer & explanation

Answer: Publish the updates to an Amazon SNS FIFO topic. Subscribe an Amazon SQS FIFO queue to the topic, and configure an AWS Lambda function to process the messages from the queue.

Answer

Publish the updates to an Amazon SNS FIFO topic, subscribe an Amazon SQS FIFO queue to the topic, and configure an AWS Lambda function to process the messages.
Utilizing an Amazon SNS FIFO topic combined with an Amazon SQS FIFO queue guarantees that messages are processed sequentially per product SKU (by using the SKU as the message group ID). This architecture ensures that stock updates are processed in the order they occurred, while AWS Lambda dynamically scales up to handle promotional traffic spikes without managing servers, minimizing operational overhead.

Step-by-Step Solution

1
Determine the decoupling and sequencing requirements.
Identified that events must be decoupled and processed in first-in, first-out order relative to each product SKU.
Sequential order prevents write conflicts and maintains inventory integrity.
2
Select the appropriate AWS messaging integration services that support ordering.
Chose Amazon SNS FIFO and Amazon SQS FIFO to route and queue updates while maintaining order.
Standard message routing options do not guarantee ordering and cannot satisfy the primary constraint.
3
Select a processing backend that minimizes operational overhead and handles sudden scale.
AWS Lambda is configured to consume batches from the SQS FIFO queue.
Lambda is serverless, requires no infrastructure provisioning, and automatically scales in response to queue depth.

Key Concept

Decoupling and ensuring sequential event processing using FIFO SNS and SQS integration patterns.
Question 367Question →

A digital ticketing platform is designing a system to process flash sale ticket purchases. The application must handle sudden surges in transaction volume and process purchase requests asynchronously. To prevent double-booking, the requests for each specific event must be processed in the exact order they were submitted. If a transaction fails to process due to downstream database timeouts, it must be isolated for manual inspection without halting the processing of other purchases.

Which solution meets these requirements with the least operational overhead?

Show answer & explanation

Answer: Send the purchase requests to an Amazon Simple Queue Service (Amazon SQS) FIFO queue. Configure the event ID as the message group ID. Set up another SQS FIFO queue as a dead-letter queue to capture failed messages after a specified number of retries.

Answer

Send the purchase requests to an Amazon Simple Queue Service (Amazon SQS) FIFO queue, configure the event ID as the message group ID, and set up an Amazon SQS FIFO queue as a dead-letter queue (DLQ).
The correct solution uses an Amazon SQS FIFO queue. Specifying the event ID as the message group ID ensures that purchases for a specific ticket event are processed sequentially, avoiding concurrent modifications or out-of-order processing that could cause double-booking. Configuring an SQS FIFO dead-letter queue (DLQ) allows failed messages to be redirected after a set number of attempts, preventing head-of-line blocking for other events and allowing administrators to inspect the failure without halting the system.

Step-by-Step Solution

1
Select the messaging service that supports FIFO ordering.
Amazon SQS FIFO queue is chosen to ensure messages within the same message group (defined by the event ID) are processed in the exact order they are received.
Standard SQS queues and Standard SNS topics do not guarantee message ordering.
2
Configure the message grouping strategy.
Set the event ID as the Message Group ID.
This ensures that transactions for the same event are processed sequentially by a single consumer, preventing double-booking, while transactions for different events can be processed in parallel.
3
Establish a mechanism to handle message processing failures without blocking the queue.
Create a secondary SQS FIFO queue as a dead-letter queue (DLQ) and configure a redrive policy on the main SQS FIFO queue.
If a transaction repeatedly fails, the redrive policy routes the message to the DLQ after a max receive count is reached. This unblocks the queue for subsequent messages in the same group, allowing manual analysis of the failed transaction.

Key Concept

Decoupling message processing using SQS FIFO queues with Message Group IDs and SQS FIFO dead-letter queues to maintain ordering and handle errors.
Question 368Question →

A global logistics company hosts its shipment tracking database on an Amazon RDS for PostgreSQL DB instance in the us-west-2 Region. The company needs to establish a disaster recovery (DR) plan in the us-east-1 Region. The DR solution must support a Recovery Point Objective (RPO) of 5 minutes and a Recovery Time Objective (RTO) of 30 minutes, while keeping ongoing costs at a minimum. Which combination of actions should a solutions architect take to meet these requirements? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Create a cross-Region read replica of the RDS DB instance in the us-east-1 Region. If a disaster occurs, promote the read replica to a standalone DB instance.; Store the application tier as an AWS CloudFormation template in Amazon S3. In the event of a disaster, deploy the application tier in the us-east-1 Region using the template, and point Amazon Route 53 to the new application endpoints.

Answer

Create a cross-Region read replica of the RDS DB instance in the us-east-1 Region and promote it during a disaster, combined with storing the application tier as an AWS CloudFormation template in Amazon S3 to deploy on-demand.
To meet the 5-minute RPO, database replication must be continuous. Creating an Amazon RDS cross-Region read replica provides asynchronous replication with a delay of seconds. During a disaster, promoting this read replica to a primary instance takes only a few minutes, meeting the 30-minute RTO. To meet the goal of minimizing costs, the application tier should not run continuously. Storing the infrastructure as an AWS CloudFormation template in Amazon S3 allows the entire application tier to be spun up on-demand in the secondary region within the 30-minute RTO window, incurring no active EC2 costs during normal operations.

Step-by-Step Solution

1
Select a replication mechanism that achieves an RPO of 5 minutes across AWS Regions.
Identify that Amazon RDS cross-Region read replicas replicate data asynchronously, typically with a lag of seconds, satisfying the 5-minute RPO requirement.
Hourly backups or multi-region synchronous replication are either too slow or unsupported for Amazon RDS.
2
Determine the database promotion strategy that fits within the 30-minute RTO.
Promoting a cross-Region read replica to a standalone primary database instance takes only a few minutes.
This meets the 30-minute RTO database-tier recovery requirement.
3
Determine the application tier recovery strategy that minimizes ongoing costs.
Keep zero active compute resources running in the disaster recovery region by storing the infrastructure definitions as AWS CloudFormation templates in Amazon S3.
This Pilot Light strategy achieves the lowest possible cost while allowing the environment to be deployed within the 30-minute RTO.

Key Concept

Disaster recovery (DR) strategies on AWS vary in cost, RTO, and RPO. Cross-Region read replicas meet low RPOs for databases by performing asynchronous replication, while Pilot Light strategies (like deploying via CloudFormation templates on-demand) minimize compute costs in the secondary region at the expense of a slightly higher RTO.
Estimated Time:1m 30s
Question 369Question →

A food delivery platform hosts its order dispatch application in the us-west-2 Region. The application tier runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer, and the database tier uses an Amazon RDS for PostgreSQL Multi-AZ DB instance. The company wants to establish a disaster recovery (DR) solution in the us-east-1 Region. The solution must achieve a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 5 minutes, while keeping ongoing standby costs as low as possible. Which disaster recovery strategy should a solutions architect recommend to meet these requirements?

Show answer & explanation

Answer: Deploy a scaled-down Auto Scaling group of EC2 instances behind an Application Load Balancer in the destination region. Create an Amazon RDS cross-region read replica in the destination region. Configure Route 53 failover routing with health checks. In the event of a disaster, promote the read replica to a primary DB instance and scale up the Auto Scaling group.

Answer

Deploy a scaled-down Auto Scaling group of EC2 instances in the destination region, create an Amazon RDS cross-region read replica, configure Route 53 failover routing, and promote the replica and scale up the instances during a disaster.
The correct strategy is a Warm Standby deployment. By keeping a scaled-down Auto Scaling group of EC2 instances running in the destination region, the application can start serving traffic immediately upon failover and then scale out. The Amazon RDS cross-region read replica maintains a near real-time copy of the database, ensuring the 5-minute RPO is met. During a disaster, the replica is promoted to primary and the EC2 instances are scaled up, which can be accomplished within the 15-minute RTO.

Step-by-Step Solution

1
Evaluate RPO requirements against replication options.
An RPO of 5 minutes requires continuous replication. An Amazon RDS cross-region read replica provides asynchronous replication with lag typically under a few seconds, meeting the 5-minute RPO.
Backup-and-restore or snapshot copy methods cannot guarantee a 5-minute RPO due to the frequency of snapshots.
2
Evaluate RTO requirements against compute standby options.
An RTO of 15 minutes is very tight. Bootstrapping new EC2 instances from scratch (desired capacity 0) takes time to launch, run user data scripts, and pass load balancer health checks. Keeping a scaled-down Auto Scaling group with at least one active instance allows immediate traffic handling while the group scales up.
Distinguishing between Warm Standby (scaled-down active instances) and Pilot Light (no running instances) is critical for meeting short recovery times.
3
Determine the routing and failover mechanics.
Configure Route 53 failover routing with health checks to detect primary region failure. In a disaster, the read replica must be promoted manually or via automation, and the standby Auto Scaling group must be scaled up to handle production traffic.
RDS cross-region replication is not automatic and requires promotion to become a read-write primary database.

Key Concept

Warm Standby Disaster Recovery Strategy
Estimated Time:2m 0s
Question 370Question →

A health insurance company is designing an asynchronous claim processing system. The system must process incoming claims in the exact order they are received to ensure compliance with auditing standards. If a claim fails to process successfully after multiple retries, it must be isolated for manual investigation without stopping or delaying the processing of subsequent claims. Which TWO components should the solutions architect combine to meet these requirements? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: An Amazon SQS FIFO queue to buffer incoming claims; A dead-letter queue (DLQ) configured on the Amazon SQS queue

Answer

An Amazon SQS FIFO queue to buffer incoming claims, combined with a dead-letter queue (DLQ) configured on the Amazon SQS queue.
The correct answer combines an Amazon SQS FIFO queue with a dead-letter queue. The SQS FIFO queue guarantees that message ordering is strictly preserved. Configuring a dead-letter queue on the SQS queue ensures that any claim failing to process after multiple attempts is redirected to the DLQ, freeing up the pipeline and preventing head-of-line blocking.

Step-by-Step Solution

1
Select a message queue that guarantees message ordering.
Amazon SQS FIFO queue is chosen over standard SQS to ensure first-in, first-out sequence for audit compliance.
Standard queues do not guarantee strict message ordering, while FIFO queues guarantee message delivery order.
2
Configure error isolation to prevent head-of-line blocking.
A dead-letter queue (DLQ) is attached to the primary SQS FIFO queue with a redrive policy.
If a claim consistently fails to process, the redrive policy routes it to the DLQ after maxReceiveCount is exceeded, permitting subsequent messages to continue processing.

Key Concept

Decoupling message-driven architectures that require strict processing order and fault isolation using SQS FIFO and DLQs.
Question 371Question →

A logistics company uses a microservices-based application to track cargo pallet lifecycle events such as received, scanned, sorted, and loaded. If these updates are processed out of sequence, the inventory database becomes corrupted. The company needs to decouple the ingestion service from the backend database while ensuring that the updates for each individual pallet are processed in the exact chronological order in which they were generated. Which solution meets these requirements with the least operational overhead?

Show answer & explanation

Answer: Publish the updates to an Amazon SQS FIFO queue, using the pallet ID as the message group ID, and use consumer instances to process the messages.

Answer

Publishing the updates to an Amazon SQS FIFO queue, using the pallet ID as the message group ID, and using consumer instances to process the messages is the correct solution.
Publishing the updates to an Amazon SQS FIFO queue ensures that messages are processed in the exact order they are received. Using the pallet ID as the message group ID ensures that events for any single pallet are processed sequentially, preventing database corruption, while enabling parallel processing of different pallets across multiple consumers.

Step-by-Step Solution

1
Analyze the ordering and decoupling requirements.
The application requires message decoupling and strict message ordering per pallet to prevent database corruption.
If messages are processed out of order, the inventory status of a pallet will become incorrect.
2
Evaluate Amazon SQS queue options for ordering guarantees.
Select Amazon SQS FIFO queues instead of SQS Standard queues.
SQS Standard queues only offer best-effort ordering, whereas SQS FIFO queues guarantee that messages are processed in the exact order they are received.
3
Configure the partitioning/grouping strategy for concurrent processing.
Use the pallet ID as the Message Group ID on the SQS FIFO queue.
This guarantees that updates for the same pallet are processed in order, while allowing different pallets to be processed concurrently by multiple consumers.

Key Concept

Amazon SQS FIFO queues provide first-in, first-out delivery. By using Message Group IDs, you can group messages so that messages within the same group are processed in order, while allowing multiple consumer instances to process different groups in parallel.
Question 372Question →

An automotive fleet telematics company processes vehicle telemetry data in the us-east-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 MySQL Multi-AZ DB instance. The company needs to design a disaster recovery (DR) strategy in the us-west-2 Region with a Recovery Time Objective (RTO) of 2 hours and a Recovery Point Objective (RPO) of 15 minutes. The solution must minimize costs during normal operations.

Which combination of actions should a solutions architect recommend to meet these requirements? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Configure Amazon RDS cross-Region replication to maintain a read replica in the secondary Region, which will be promoted to a standalone primary database during a failover event.; Prepare an AWS CloudFormation template containing the application tier resources, and deploy it in the secondary Region with the Auto Scaling group's desired capacity set to 0.

Answer

Configure Amazon RDS cross-Region replication to maintain a read replica in the secondary Region to be promoted during failover, and prepare an AWS CloudFormation template to deploy the application tier in the secondary Region with the Auto Scaling group desired capacity set to 0.
The correct strategy combines database replication and compute infrastructure preparedness. Configuring Amazon RDS cross-Region replication provides continuous asynchronous data transfer to the secondary Region, satisfying the 15-minute RPO. Deploying the application tier infrastructure with an Auto Scaling group capacity of 0 ensures that no EC2 compute charges are incurred during normal operations. In a disaster recovery event, the solutions architect can promote the RDS read replica to a primary database and scale up the Auto Scaling group, recovering the application stack well within the 2-hour RTO.

Step-by-Step Solution

1
Address the 15-minute database RPO with asynchronous cross-Region database replication.
Create an Amazon RDS cross-Region read replica of the MySQL database in the target Region.
RDS cross-Region read replicas replicate changes asynchronously within seconds or minutes, guaranteeing the data loss remains well below the 15-minute target.
2
Minimize compute costs during normal operations while satisfying the 2-hour RTO.
Deploy an AWS CloudFormation template in the target Region with the Auto Scaling group capacity set to 0.
Keeping the Auto Scaling group capacity at 0 ensures that no EC2 instances are running or billed during standard operations, matching the Pilot Light strategy. During a disaster, the capacity is updated to scale up the instances.
3
Ensure the overall recovery process can complete within the 2-hour RTO limit.
Define recovery steps: promote the RDS read replica to primary and increase the Auto Scaling group desired capacity.
Promoting the read replica and launching EC2 instances via Auto Scaling takes under 15 minutes, which successfully satisfies the 2-hour RTO requirement.

Key Concept

Implementing a cost-optimized Pilot Light disaster recovery strategy across Regions using Amazon RDS cross-Region read replicas and scaled-down Auto Scaling groups.
Estimated Time:2m 0s
Question 373Question →

A municipal energy utility company hosts its customer billing portal in the eu-west-1 Region. The application tier runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer (ALB). The database tier uses an Amazon RDS for PostgreSQL DB instance. The company needs to design a disaster recovery (DR) strategy in the eu-central-1 Region. The solution must achieve a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 5 minutes, while minimizing ongoing costs. Which architecture should a solutions architect recommend to meet these requirements?

Show answer & explanation

Answer: Configure an Amazon RDS cross-region read replica in the secondary region. Deploy a scaled-down Auto Scaling group of EC2 instances behind an Application Load Balancer in the secondary region. In the event of a disaster, promote the cross-region read replica to a standalone database instance, scale up the Auto Scaling group, and update Amazon Route 53 failover routing records to point to the secondary Application Load Balancer.

Answer

Configure an Amazon RDS cross-region read replica in the secondary region, deploy a scaled-down Auto Scaling group of EC2 instances behind an Application Load Balancer in the secondary region, and in the event of a disaster, promote the replica, scale up the Auto Scaling group, and update Route 53 failover routing.
A Warm Standby DR strategy is the most cost-effective solution that satisfies both the 15-minute RTO and 5-minute RPO. The cross-region read replica replicates data asynchronously, keeping the RPO under 5 minutes. The scaled-down Auto Scaling group keeps EC2 costs low while ensuring that virtual machines are pre-provisioned and can be scaled up immediately to meet the RTO. Manual promotion of the RDS read replica is required to make the secondary database active for write operations.

Step-by-Step Solution

1
Establish cross-region database replication to meet the RPO requirement.
Create an Amazon RDS cross-region read replica in the secondary region (eu-central-1) to asynchronously replicate the primary PostgreSQL DB instance.
Asynchronous replication runs continuously, keeping the replication lag to seconds or minutes, which satisfies the 5-minute RPO.
2
Set up the application tier in the recovery region to meet the RTO requirement cost-effectively.
Deploy an Application Load Balancer and a scaled-down Auto Scaling group of EC2 instances in the secondary region.
Keeping a Warm Standby (scaled-down Auto Scaling group and ALB) minimizes ongoing costs while ensuring the core compute infrastructure is already online and ready to scale up within minutes.
3
Orchestrate failover in the event of a primary region outage.
Promote the RDS cross-region read replica to a standalone DB instance, scale up the EC2 Auto Scaling group to production size, and update Route 53 DNS records to point to the secondary ALB.
Promoting the read replica and scaling up the existing compute capacity allows the environment to become fully active and handle production traffic within the 15-minute RTO.

Key Concept

Warm Standby Disaster Recovery Strategy
Estimated Time:1m 30s
Question 374Question →

A smart wearable device company is designing a system to process user workout telemetry events (such as activity started, heart rate milestone, activity paused, and activity completed) from fitness trackers. The events must be processed in the exact chronological sequence they are generated for each individual user workout. The backend processing application is deployed on Amazon EC2 instances. During peak hours, the backend database occasionally experiences lock contention, causing temporary processing failures. If a telemetry event fails to process, the system must retry it. If it fails 5 times, it must be isolated for analysis without blocking subsequent events for that user's workout or other users' workouts.

Which solution meets these requirements with the least operational overhead?

Show answer & explanation

Answer: Publish the workout events to an Amazon SQS FIFO queue, using the workout ID as the message group ID. Configure the backend EC2 instances to consume messages from the queue. Set up a dead-letter queue (DLQ) with a redrive policy on the primary SQS FIFO queue to capture failed messages after a maximum receive count of 5.

Answer

Publish the workout events to an Amazon SQS FIFO queue, using the workout ID as the message group ID. Configure the backend EC2 instances to consume messages from the queue. Set up a dead-letter queue (DLQ) with a redrive policy on the primary SQS FIFO queue to capture failed messages after a maximum receive count of 5.
The correct answer provides in-order event processing per user workout by using an Amazon SQS FIFO queue with a message group ID. Using a dead-letter queue (DLQ) with a maxReceiveCount of 5 handles failures by isolating problematic messages after multiple attempts without halting the processing of other messages.

Step-by-Step Solution

1
Select SQS FIFO over standard queues to maintain strict message ordering.
Ensures that events for a specific workout are processed chronologically.
Standard SQS queues only provide best-effort ordering, whereas FIFO guarantees first-in, first-out delivery.
2
Use the workout ID as the message group ID.
Enables parallel processing of different workouts while maintaining ordering within each individual workout.
Messages belonging to the same message group are always processed in order relative to each other.
3
Configure a dead-letter queue (DLQ) with a maxReceiveCount of 5.
Isolates poison pill messages after 5 failed processing attempts.
Prevents unprocessable messages from blocking the rest of the queue, allowing other workloads to proceed.

Key Concept

Decoupled architecture using SQS FIFO queues with a DLQ for ordered, resilient processing.
Estimated Time:1m 30s
Question 375Question →

A restaurant chain is implementing a cloud-based kitchen display system. When a customer places an order, the order details must be sent to the kitchen terminal and to a real-time analytics dashboard. The kitchen terminal must receive and display orders in the exact sequence they were submitted by the customer. The analytics dashboard does not require strict ordering. If an order fails to process after multiple attempts, it must be isolated for troubleshooting with the least operational overhead.

Which combination of steps should a solutions architect take to meet these requirements? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Create an Amazon SNS FIFO topic. Create an Amazon SQS FIFO queue for the kitchen terminal and a standard Amazon SQS queue for the analytics dashboard. Subscribe both queues to the SNS FIFO topic.; Configure a redrive policy on the SQS queues to send failed messages to a dead-letter queue (DLQ) after the maximum receive count is exceeded.

Answer

Create an Amazon SNS FIFO topic, create an Amazon SQS FIFO queue for the kitchen terminal, subscribe both queues to the SNS FIFO topic, and configure a redrive policy on the SQS queues to send failed messages to a dead-letter queue (DLQ).
To achieve both event fan-out and strict ordering for one of the downstream consumers, the architect must combine an Amazon SNS FIFO topic with an Amazon SQS FIFO queue. SNS FIFO topics support fanning out messages to multiple SQS queues. By subscribing an SQS FIFO queue for the ordering-sensitive kitchen terminal and a standard SQS queue for the analytics dashboard (which does not require strict ordering), both consumers receive the messages appropriately. Furthermore, configuring a redrive policy on the SQS queues allows messages that repeatedly fail processing to be automatically sent to a dead-letter queue (DLQ) for isolation and troubleshooting with minimal operational overhead.

Step-by-Step Solution

1
Analyze the fan-out and ordering requirements.
Identified that the system requires sending a single event to two different consumers (fan-out pattern) with one consumer requiring strict message ordering (FIFO).
This determines that Amazon SNS is needed for fan-out and FIFO capabilities are required for ordering.
2
Select the correct SNS and SQS queue types.
Choose an Amazon SNS FIFO topic to publish events. For the kitchen terminal, select an Amazon SQS FIFO queue. For the analytics dashboard, select a standard Amazon SQS queue. Subscribe both queues to the SNS FIFO topic.
SNS FIFO topics can fan out to both SQS FIFO and standard SQS queues, preserving order for the FIFO queue while delivering to both.
3
Address the processing failure isolation requirement.
Configure a redrive policy on the SQS queues to direct failed messages to an SQS dead-letter queue (DLQ) after a specified maximum receive count.
SQS redrive policies isolate messages that fail application-level processing after multiple retries.

Key Concept

Decoupling message fan-out with ordering guarantees using Amazon SNS FIFO and SQS FIFO queues.
Question 376Question →

A smart home IoT monitoring service hosts its primary application in the us-east-1 Region. The architecture consists of Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer, an Amazon RDS for PostgreSQL database, and static configuration files stored in an Amazon S3 bucket.

The company needs to establish a disaster recovery (DR) site in the us-west-2 Region. The DR solution must achieve a Recovery Time Objective (RTO) of 2 hours and a Recovery Point Objective (RPO) of 15 minutes, while minimizing ongoing infrastructure costs.

Which combination of actions should the solutions architect take to meet these requirements? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Set up an Amazon RDS cross-region read replica in the secondary region, and configure Amazon S3 Cross-Region Replication (CRR) to copy static files to the secondary region.; Deploy an Application Load Balancer and configure an Auto Scaling group with the desired capacity set to zero in the secondary region, and ensure application Amazon Machine Images (AMIs) are pre-copied to the secondary region.

Answer

Setting up an Amazon RDS cross-region read replica and Amazon S3 Cross-Region Replication (CRR) ensures data is replicated asynchronously to meet the 15-minute RPO. Pre-configuring the Application Load Balancer and an Auto Scaling group with zero capacity in the secondary region establishes a Pilot Light strategy that minimizes baseline cost while allowing full scaling within the 2-hour RTO.
The correct combination of actions uses a Pilot Light disaster recovery strategy to achieve the RTO and RPO goals cost-effectively. Creating an Amazon RDS cross-region read replica and configuring Amazon S3 Cross-Region Replication (CRR) ensures data is replicated asynchronously to the secondary region with minimal lag, satisfying the 15-minute RPO. Pre-configuring the Application Load Balancer and Auto Scaling group with desired capacity set to zero in the secondary region ensures compute costs are not incurred until a failover is initiated. Upon failover, the database replica is promoted and the Auto Scaling group is scaled up, which can be accomplished well within the 2-hour RTO.

Step-by-Step Solution

1
Analyze RTO, RPO, and cost constraints.
RTO is 2 hours (allows time to provision compute and promote databases), RPO is 15 minutes (requires continuous or highly frequent asynchronous replication), and costs must be minimized (favors Pilot Light or Warm Standby with resources scaled down).
Understanding the recovery boundaries is necessary to select the appropriate disaster recovery pattern.
2
Select the database and storage replication mechanism that satisfies the 15-minute RPO.
Amazon RDS cross-region read replicas use asynchronous replication with very low lag (usually seconds), meeting the 15-minute RPO. Amazon S3 Cross-Region Replication (CRR) replicates objects asynchronously, also meeting the 15-minute RPO.
This satisfies the data persistence requirements across regions within the allowed data loss envelope.
3
Select the compute staging mechanism that meets the 2-hour RTO while minimizing costs.
Deploying the Application Load Balancer and configuring the Auto Scaling group with the desired capacity set to zero minimizes compute costs, as no EC2 instances run during normal operations. Scaling up the group during failover takes minutes, fitting comfortably inside the 2-hour RTO.
This ensures the application layer is ready to be provisioned quickly without incurring active running costs.

Key Concept

Disaster Recovery (DR) strategies on AWS (specifically Pilot Light vs. Warm Standby / Hot Standby) and cross-region replication mechanisms for RDS and S3.
Question 377Question →

A logistics telemetry company hosts its fleet tracking application in the us-east-1 Region. The architecture consists of Amazon EC2 instances in an Auto Scaling Group behind an Application Load Balancer, and a primary Amazon RDS for PostgreSQL database instance. The company needs to design a disaster recovery (DR) plan in the us-west-2 Region. The DR plan must support a Recovery Time Objective (RTO) of 1515 minutes, a Recovery Point Objective (RPO) of 55 minutes, and minimize ongoing infrastructure costs. Which DR strategy meets these requirements?

Show answer & explanation

Answer: Establish a Pilot Light recovery environment in us-west-2. Configure an RDS cross-region read replica in us-west-2. Deploy an Elastic Load Balancer and an Auto Scaling Group with a desired capacity of 00. During a disaster, promote the read replica to a standalone database and scale the Auto Scaling Group to the required production capacity.

Answer

Establish a Pilot Light recovery environment in us-west-2 by configuring an RDS cross-region read replica and an Auto Scaling Group with a desired capacity of 00, then promoting the replica and scaling the Auto Scaling Group during a disaster.
The correct strategy uses Pilot Light. An Amazon RDS cross-region read replica provides asynchronous replication with very low lag (usually seconds), easily meeting the 55-minute RPO. In the event of a disaster, the replica is promoted to a primary database, and the Auto Scaling Group is scaled up from 00 to the required capacity. This sequence completes within the 1515-minute RTO. Because no EC2 instances run in the recovery region during normal operation, this approach minimizes ongoing costs.

Step-by-Step Solution

1
Evaluate the RTO and RPO requirements against the DR strategies.
An RPO of 55 minutes requires active database replication. S3 backups copied hourly (with Glacier retrieval times) fail the RPO. An RTO of 1515 minutes allows for either Warm Standby or Pilot Light, as both can scale up or promote databases within this window.
Eliminates Backup and Restore options which cannot meet the RPO of 55 minutes or the RTO of 1515 minutes.
2
Evaluate the database replication capability across AWS regions.
RDS Multi-AZ is a single-region high-availability feature and cannot place a standby replica in a different AWS region.
Eliminates the option proposing cross-region Multi-AZ standby replication.
3
Compare Pilot Light and Warm Standby based on the cost minimization constraint.
Pilot Light keeps the application tier shutdown (desired capacity of 00 for ASG), which incurs zero EC2 compute costs during idle periods. Warm Standby keeps a minimum number of EC2 instances running, incurring continuous compute costs. Route 53 latency routing also fails to provide failover without health checks.
Identifies the Pilot Light option as the most cost-effective solution that meets all constraints.

Key Concept

Disaster Recovery (DR) strategies using Pilot Light with cross-region read replicas to meet tight RTO/RPO targets while minimizing idle costs.
Estimated Time:2m 0s
Question 378Question →

A digital ticketing platform experiences massive traffic spikes when tickets for popular events go on sale. The platform must process ticket reservation requests in the exact order they are received to prevent overbooking. The platform's relational database cannot handle the sudden spike in write requests directly. Which solution decouples the ingestion layer from the database while maintaining strict message ordering?

Show answer & explanation

Answer: Use an Amazon SQS FIFO queue to buffer the reservation requests, and configure an AWS Lambda function to process the messages and update the database.

Answer

Use an Amazon SQS FIFO queue to buffer the reservation requests, and configure an AWS Lambda function to process the messages and update the database.
The correct solution uses an Amazon SQS FIFO queue to buffer reservation requests. SQS FIFO queues guarantee that messages are processed in the exact order they are received and prevent duplicates. An AWS Lambda function can poll the queue to process messages at a controlled rate, successfully protecting the database from write spikes while maintaining transaction ordering.

Step-by-Step Solution

1
Analyze ordering requirements
Identify that the system requires strict first-in, first-out (FIFO) delivery to ensure reservations are processed in order and prevent overbooking.
Correctly identifying ordering requirements guides the choice between standard and FIFO services.
2
Analyze decoupling and buffering requirements
Determine that the database cannot handle sudden write spikes, requiring a queuing mechanism that supports message buffering.
Decoupling with a queue protects downstream databases from throttling and performance degradation.
3
Select the correct integration pattern
Choose Amazon SQS FIFO queue combined with AWS Lambda to process the buffered messages in order.
SQS FIFO guarantees ordering and deduplication, while Lambda consumes messages sequentially within the message group.

Key Concept

Using Amazon SQS FIFO queues to guarantee strict order processing and decouple components under heavy load.
Estimated Time:1m 30s
Question 379Question →

A SaaS company hosts an enterprise human resources (HR) portal in the ap-southeast-2 Region. The architecture consists of Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer, and an Amazon RDS for PostgreSQL database. The company needs to design a disaster recovery (DR) plan in the ap-southeast-1 Region. The DR plan must support a recovery time objective (RTO) of 30 minutes and a recovery point objective (RPO) of 5 minutes, while minimizing ongoing running costs.

Which combination of steps should a solutions architect recommend to meet these requirements? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Create an Amazon RDS for PostgreSQL cross-region read replica in the disaster recovery region.; Replicate the application server Amazon Machine Images (AMIs) to the disaster recovery region, and create an Auto Scaling group with a desired capacity of zero.

Answer

To meet the requirements, the solutions architect must configure an Amazon RDS cross-region read replica in the disaster recovery region and replicate the application AMIs to set up an Auto Scaling group with a desired capacity of zero.
The correct options implement a cost-effective Pilot Light strategy. The RPO of 5 minutes is met by creating an Amazon RDS cross-region read replica, which continuously replicates database transactions asynchronously with minimal lag. The RTO of 30 minutes allows the application tier to remain offline (zero running instances) to minimize costs. In a disaster recovery event, the read replica is promoted to a primary database and the Auto Scaling group is scaled up from zero using the replicated AMIs, completing the entire failover well within the 30-minute window.

Step-by-Step Solution

1
Configure database replication for low RPO.
Create a cross-region read replica of the PostgreSQL DB in the ap-southeast-1 region.
Asynchronous cross-region read replicas satisfy the 5-minute RPO by keeping the recovery database up-to-date with minimal replication lag.
2
Minimize recovery region compute costs.
Copy application AMIs to the target region and deploy an Auto Scaling group set to zero instances.
Setting the capacity to zero ensures no running instances are billed during normal operations, implementing a cost-optimized Pilot Light disaster recovery strategy.
3
Define failover procedures.
Create a runbook to promote the read replica to standalone status and scale the Auto Scaling group capacity up during a disaster.
Promoting a replica and booting EC2 instances from AMIs can be completed well within the 30-minute RTO.

Key Concept

A Pilot Light disaster recovery strategy minimizes running costs by keeping compute capacity scaled to zero while maintaining active, asynchronous database replication via cross-region read replicas to meet low recovery point objectives.
Estimated Time:2m 0s
Question 380Question →

An online multiplayer gaming company hosts its matchmaking and leaderboard platform in the us-east-1 Region. The backend application runs on Amazon EC2 instances behind an Application Load Balancer (ALB), and data is stored in an Amazon RDS for PostgreSQL database. The company wants to establish a disaster recovery (DR) plan in the us-west-2 Region. The solution must meet a 3030-minute Recovery Time Objective (RTO) and a 55-minute Recovery Point Objective (RPO) while minimizing ongoing infrastructure costs. Which strategy should a solutions architect recommend to meet these requirements?

Show answer & explanation

Answer: Implement a Pilot Light recovery strategy in the us-west-2 Region. Set up Amazon RDS cross-region replication to continuously replicate database writes. Keep application servers stopped or deploy them dynamically via AWS CloudFormation and pre-configured Amazon Machine Images (AMIs) during a failover event.

Answer

Implement a Pilot Light recovery strategy in the us-west-2 Region by setting up Amazon RDS cross-region replication to continuously replicate database writes, and keeping application servers stopped or deploying them dynamically via AWS CloudFormation and pre-configured AMIs during a failover event.
The correct strategy is the Pilot Light setup. This option meets the 55-minute RPO by continuously replicating the primary database to the disaster recovery region using Amazon RDS cross-region replication. It also meets the 3030-minute RTO because application servers can be started or provisioned from pre-configured AMIs and CloudFormation templates within that time frame. Because the application compute resources are kept shut down or unprovisioned until failover, ongoing operational costs are minimized.

Step-by-Step Solution

1
Analyze the RTO and RPO requirements.
The target RTO is 3030 minutes (maximum acceptable downtime) and the target RPO is 55 minutes (maximum acceptable data loss).
This determines which DR strategy and replication technologies are viable.
2
Evaluate replication methods for the database to meet the 55-minute RPO constraint.
AWS Backup with daily backups fails the RPO. Amazon RDS cross-region read replicas continuously replicate data asynchronously, keeping data lag typically under a few minutes, which satisfies the 55-minute RPO.
Continuous database replication is required to avoid losing more than 55 minutes of data.
3
Select the most cost-effective compute deployment that satisfies the 3030-minute RTO.
A Pilot Light strategy allows compute resources (EC2 instances) to remain turned off or unprovisioned, and then started or created from AMIs within 3030 minutes. This is more cost-effective than Warm Standby, which keeps scaled-down instances running continuously.
Since the RTO is 3030 minutes, there is sufficient time to spin up instances dynamically, avoiding the cost of idle running instances.

Key Concept

Disaster Recovery strategies (Pilot Light vs. Warm Standby) and cross-region replication capabilities.
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