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Design Resilient Architectures

382 questions

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Question 321Question →

A gaming platform publishes real-time player match results. These results must be processed by two separate backend systems: a leaderboard service and an achievements service. To ensure accurate game statistics, the match results must be processed by both systems in the exact sequence they occur. Which combination of AWS services should the solutions architect select to decouple these systems while preserving the order of the match results? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Amazon Simple Notification Service (Amazon SNS) FIFO topic; Amazon Simple Queue Service (Amazon SQS) FIFO queues

Answer

Amazon Simple Notification Service (Amazon SNS) FIFO topic and Amazon Simple Queue Service (Amazon SQS) FIFO queues
To decouple the game platform from the leaderboard and achievements services while maintaining message ordering, a combination of Amazon SNS FIFO and Amazon SQS FIFO is the standard architectural pattern. The SNS FIFO topic handles the message fan-out to multiple subscribers, and the SQS FIFO queues ensure that each service consumes the messages in the exact order they were sent.

Step-by-Step Solution

1
Identify the requirement to fan out message processing to multiple independent downstream systems (leaderboard and achievements services).
An Amazon SNS topic is required to publish messages once and deliver them to multiple subscribers.
SNS provides the publish/subscribe (fan-out) capability needed to send the same event to multiple destinations.
2
Identify the requirement to maintain strict ordering of events for both downstream systems.
FIFO (First-In-First-Out) features must be enabled on both the SNS topic and the SQS queues.
Standard SNS topics and SQS queues do not guarantee message ordering, whereas FIFO variants guarantee strict ordering and deduplication.
3
Combine the services to form an ordered fan-out pattern.
The architecture will consist of an SNS FIFO topic publishing to multiple SQS FIFO queues subscribed to it.
This pattern decouples the publisher from the subscribers while ensuring both systems receive events in the exact sequence they were generated.

Key Concept

De-coupling with Fan-Out and Message Ordering
Question 322Question →

A logistics and supply chain enterprise is building a package tracking system. When a package's delivery status changes, three distinct downstream systems must be updated: a real-time customer tracking portal, an analytics data warehouse, and an automated customer SMS notification service. The sequence of status updates must be strictly preserved on a per-package basis to prevent displaying incorrect states (such as showing 'Delivered' before 'In Transit'). The SMS notification service occasionally experiences intermittent downtime, and its messages must be retried independently without delaying processing for the tracking portal or the data warehouse. Which architecture meets these requirements with the least operational overhead?

Show answer & explanation

Answer: Publish status updates to an Amazon SNS FIFO topic. Subscribe three separate Amazon SQS FIFO queues to the topic (one for each downstream system), and have each system consume messages from its respective queue.

Answer

Publish status updates to an Amazon SNS FIFO topic. Subscribe three separate Amazon SQS FIFO queues to the topic (one for each downstream system), and have each system consume messages from its respective queue.
The solution utilizing an Amazon SNS FIFO topic fanned out to three separate Amazon SQS FIFO queues successfully meets all constraints. SNS FIFO maintains ordering across the fan-out boundary, and the SQS FIFO queues maintain strict order per message group (using the package ID as the MessageGroupId). Crucially, having separate SQS FIFO queues for each service ensures that if the SMS service goes down, messages accumulate in its specific queue and can be retried independently without blocking the tracking portal or the data warehouse.

Step-by-Step Solution

1
Analyze the fan-out requirement.
The message must be fanned out to three distinct downstream consumers (customer portal, analytics warehouse, SMS service) in a decoupled manner.
This establishes that a publish-subscribe pattern is needed.
2
Analyze the ordering requirement.
Status updates must be processed strictly in sequence per package.
This requires first-in, first-out (FIFO) message processing, ruling out standard queues and topics.
3
Analyze retry and outage isolation.
One downstream consumer (SMS service) experiences downtime. Its failures must be retried without impacting the other two consumers.
Each consumer needs its own dedicated queue so that backlogs or errors in one consumer do not affect the throughput of the others.
4
Select the optimal serverless AWS services.
Amazon SNS FIFO fanning out to multiple Amazon SQS FIFO queues provides both ordered delivery and isolated buffering with minimal operational overhead.
This avoids the operational complexity of managing custom consumer groups in Kinesis or writing complex retry logic in a coupled Lambda function.

Key Concept

Combining Amazon SNS FIFO and Amazon SQS FIFO queues in tandem allows for ordered message fan-out and decoupled consumer processing, isolating failures and retries for individual subscribers.
Estimated Time:2m 30s
Question 323Question →

A company is building a ride-sharing application. The application must process passenger ride-status updates, such as requested, driver assigned, and completed, asynchronously. To ensure the passenger history displays correctly, these updates must be processed in the exact sequence they occurred. The system processes approximately 150 updates per second. Which solution meets these requirements with the least operational overhead?

Show answer & explanation

Answer: Send the ride-status update messages to an Amazon SQS FIFO queue and process them sequentially.

Answer

Send the ride-status update messages to an Amazon SQS FIFO queue and process them sequentially.
The correct option correctly identifies Amazon SQS FIFO queues as the native AWS solution to guarantee that messages are processed in the exact order they are received. Since the application processes 150 updates per second, it falls well within the default limit of 300 transactions per second for FIFO queues without batching, satisfying the request with minimal operational complexity.

Step-by-Step Solution

1
Analyze the requirements for message ordering and throughput.
The application requires strict first-in, first-out (FIFO) ordering for ride-status updates at a rate of 150 updates per second.
This determines whether a standard queue or a FIFO queue is required.
2
Evaluate the capabilities of Amazon SQS queue types.
Amazon SQS FIFO queues guarantee order preservation and support up to 300 transactions per second (TPS) without batching, which exceeds the required 150 updates per second. Amazon SQS Standard queues do not guarantee ordering.
This identifies the only queue type that natively supports the strict ordering constraint without custom sorting logic.
3
Select the solution with the least operational overhead.
Using an Amazon SQS FIFO queue natively fulfills the ordering requirement without requiring additional consumer sorting logic or complex custom applications.
This satisfies the requirement to minimize operational overhead.

Key Concept

Amazon SQS FIFO queues preserve the exact ordering of messages and are ideal for low-to-medium throughput applications requiring strict sequencing.
Estimated Time:45s
Question 324Question →

A company wants to set up a disaster recovery (DR) solution for its database in a secondary AWS Region. The solution must support a Recovery Point Objective (RPO) of 24 hours and a Recovery Time Objective (RTO) of 24 hours. The company wants to minimize costs and does not want to run any active database instances in the secondary Region during normal operations. Which DR strategy meets these requirements?

Show answer & explanation

Answer: Backup and restore by copying database snapshots to the secondary Region

Answer

Backup and restore by copying database snapshots to the secondary Region
The correct answer is the option that suggests backup and restore by copying snapshots. Backup and Restore is the most cost-effective DR strategy. Backups (snapshots) of the database are copied to a secondary Region. No active database or compute resources run in the secondary Region under normal conditions, which meets the cost requirement. When a disaster occurs, the database is restored from the snapshot, which can comfortably be completed within the 24-hour RTO.

Step-by-Step Solution

1
Analyze the requirements for RPO, RTO, and cost.
The target RPO is 24 hours, the RTO is 24 hours, and there must be zero running compute/database costs in the secondary region.
This establishes the boundaries for evaluating the DR options.
2
Evaluate the Backup and Restore strategy against the constraints.
Backup and Restore keeps only backups in the secondary region and creates resources only when a disaster occurs, which aligns with zero running database instances and is the most cost-effective solution.
To verify if the cheapest option meets the recovery timeline.

Key Concept

Disaster Recovery strategies (Backup & Restore, Pilot Light, Warm Standby, Multi-Site) differ in RTO, RPO, and cost.
Question 325Question →

A digital media platform is designing an event-driven news publishing system. When an editor publishes or updates an article, the system must broadcast the event to two backend services: a real-time mobile push notification service and an article search indexing service. The push notification service can process events in any order. However, the search indexing service must process updates for each article in the exact chronological sequence they were published to avoid indexing stale data. The system must automatically scale to handle traffic spikes without administrative intervention. Which combination of actions 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 and publish article update events to it, using the article ID as the message group ID.; Create two Amazon SQS FIFO queues, subscribe both queues to the SNS FIFO topic, and configure each backend service to consume from its respective queue.

Answer

Create an Amazon SNS FIFO topic with the article ID as the message group ID, and subscribe two Amazon SQS FIFO queues to it so each backend service can consume from its own dedicated queue.
To maintain message sequence across a fan-out architecture, an Amazon SNS FIFO topic must be paired with Amazon SQS FIFO queues. The SNS FIFO topic preserves the order of messages sent by the publisher, and specifying the article ID as the Message Group ID ensures that updates for the same article are processed in order. Since SNS FIFO topics only support SQS FIFO queues as subscribers, both subscription queues must be FIFO queues.

Step-by-Step Solution

1
Analyze the fan-out and ordering requirements.
The architecture requires sending the same publishing event to multiple consumers (fan-out), where one consumer requires strict sequence ordering per article.
Identifying that a single publisher needs to distribute messages to multiple decoupled consumers helps select a publish-subscribe pattern using Amazon SNS and Amazon SQS.
2
Determine the appropriate Amazon SNS topic configuration.
Select an Amazon SNS FIFO topic and publish events using the article ID as the Message Group ID.
Standard SNS topics do not guarantee ordering. An SNS FIFO topic ensures message ordering is preserved within a message group, preventing race conditions or stale updates for a given article.
3
Identify the queue subscription requirements.
Create two Amazon SQS FIFO queues and subscribe both to the SNS FIFO topic.
Amazon SNS FIFO topics only support Amazon SQS FIFO queues as subscribers. SQS Standard queues cannot be subscribed to an SNS FIFO topic, meaning both destination queues must be FIFO to maintain end-to-end ordered delivery.

Key Concept

Amazon SNS FIFO and Amazon SQS FIFO integration for ordered message fan-out.
Estimated Time:2m 0s
Question 326Question →

A company operates a food delivery dispatch platform in the us-east-1 Region. The architecture utilizes Amazon ECS on AWS Fargate for the microservices and an Amazon RDS for PostgreSQL Multi-AZ DB instance for the transactional database. The company needs to implement a disaster recovery (DR) strategy in the us-west-2 Region. The DR solution must achieve a Recovery Time Objective (RTO) of 30 minutes, a Recovery Point Objective (RPO) of 5 minutes, and minimize ongoing running costs in the secondary Region. Which strategy should a solutions architect recommend to meet these requirements?

Show answer & explanation

Answer: Configure an RDS for PostgreSQL cross-region read replica in the us-west-2 Region. Deploy an Application Load Balancer (ALB) in us-west-2 and configure an ECS service with a desired task count of zero. Set up Amazon Route 53 with failover routing and health checks. During a disaster, promote the read replica to a standalone DB instance, update the ECS service desired count to match production levels, and let Route 53 redirect traffic to the secondary ALB.

Answer

Configure an RDS for PostgreSQL cross-region read replica, set the secondary ECS task count to zero, use Route 53 failover routing with health checks, and promote the replica and scale up tasks during a failover event.
The correct strategy uses a Pilot Light approach. A cross-region RDS read replica replicates data asynchronously, keeping the RPO to a few seconds, which satisfies the 5-minute requirement. Running the secondary ECS service with a desired task count of zero minimizes running costs. Promoting the database to primary status and scaling up the ECS service tasks to production levels can be done in a few minutes, satisfying the 30-minute RTO.

Step-by-Step Solution

1
Select database replication strategy based on the RPO of 5 minutes.
Determine that an RDS cross-region read replica is necessary to continuously replicate data, ensuring data loss remains under 5 minutes.
Hourly backups or snapshots copied to another region would violate the 5-minute RPO limit.
2
Select the compute layer deployment strategy to minimize standby costs while meeting the 30-minute RTO.
Deploy an ALB and configure the secondary Region's ECS service with a desired task count of 0.
An active but scaled-down fleet increases running costs needlessly. Launching and scaling ECS Fargate tasks can be completed within minutes during a failover, well within the 30-minute limit.
3
Configure the DNS routing and failover automation.
Configure Route 53 failover routing with health checks pointing to the primary ALB, and define the manual or scripted steps to promote the RDS read replica and scale up the ECS tasks.
Active-active latency routing without health checks fails to steer traffic away from the degraded primary region.

Key Concept

Disaster Recovery (DR) Pilot Light Pattern on AWS
Question 327Question →

A company has a web application that processes user registration requests. The requests must be processed asynchronously in the exact order they are received to ensure proper database indexing. The workload is highly unpredictable with sudden, massive traffic spikes. A solutions architect needs to decouple the frontend application from the backend processing servers. Which solution meets these requirements with the least operational overhead?

Show answer & explanation

Answer: Configure the web application to send the requests to an Amazon SQS FIFO queue, and configure backend servers to process the messages.

Answer

Configure the web application to send the requests to an Amazon SQS FIFO queue, and configure backend servers to process the messages.
The correct option is the one that configures the application to use Amazon SQS FIFO queues. FIFO queues guarantee that messages are processed in the exact order they are sent, satisfying the indexing requirement. Because SQS scales automatically to absorb spikes, it buffers the load for the backend servers, meeting the decoupling and resilience goals with the least operational overhead.

Step-by-Step Solution

1
Analyze the requirement for message ordering.
The messages must be processed in the exact order they are received to ensure proper database indexing.
This requirement rules out standard queue systems that do not guarantee ordering.
2
Evaluate Amazon SQS queue types.
Amazon SQS FIFO queues guarantee first-in, first-out delivery and single execution.
FIFO queues meet the ordering requirement while decoupling the application components.
3
Verify handling of unpredictable traffic spikes.
Amazon SQS automatically scales to handle spikes in traffic without manual provisioning.
This provides a highly resilient architecture with minimal operational overhead.

Key Concept

Decoupling with ordered message processing using SQS FIFO queues
Question 328Question →

A company hosts a web application in the us-east-1 Region. The application stores static media files in an Amazon S3 bucket and uses an Amazon RDS for PostgreSQL database. To prepare for a disaster recovery (DR) scenario, the company wants to implement a Backup and Restore DR strategy in the us-west-2 Region. Which TWO options should a solutions architect recommend to copy the S3 objects and database backups to the secondary region?

Select all that apply

Show answer & explanation

Answer: Enable Amazon S3 Cross-Region Replication (CRR) on the source S3 bucket to replicate new object uploads to a destination bucket in the secondary region.; Configure AWS Backup to automatically replicate Amazon RDS database backups and snapshots to the secondary region.

Answer

The correct options are enabling Amazon S3 Cross-Region Replication (CRR) and using AWS Backup to replicate database backups to the secondary region.
For a Backup and Restore disaster recovery strategy, the primary goal is to copy backups to a secondary region. Enabling Amazon S3 Cross-Region Replication (CRR) handles S3 objects automatically, while AWS Backup handles replicating RDS snapshots to the target region. Both solutions keep replication simple without requiring running database instances in the recovery region.

Step-by-Step Solution

1
Select the correct replication method for S3 data.
Identify that S3 Cross-Region Replication (CRR) automatically replicates objects across regions.
S3 CRR is the standard and most efficient way to keep static files synchronized across different regions with minimal operational overhead.
2
Select the correct replication method for database backups.
Identify that AWS Backup is the standard managed service to copy RDS backups across regions automatically.
Using AWS Backup simplifies cross-region copy operations and centralized backup compliance management.
3
Evaluate and eliminate incorrect architectures.
Eliminate options proposing automatic failover to read replicas, S3 Glacier for quick retrieval, and running a fully-scaled instance under a Pilot Light model.
These options contain configuration misconceptions regarding RDS cross-region behavior, Glacier retrieval latencies, and DR tier definitions.

Key Concept

Disaster recovery data replication
Estimated Time:1m 0s
Question 329Question →

A medical imaging provider hosts its diagnostic report processing application in the us-west-2 Region. The current architecture consists of EC2 instances in an Auto Scaling group behind an Application Load Balancer, and a multi-AZ Amazon Aurora PostgreSQL database. The provider needs to establish a disaster recovery (DR) strategy in the us-east-1 Region. The DR solution must achieve a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 2 minutes, while minimizing ongoing infrastructure 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: Create an Amazon Aurora Global Database with the primary cluster in us-west-2 and a secondary cluster in us-east-1, configuring the secondary cluster to use Aurora Serverless v2 to scale down to a minimal configuration during idle periods.; Pre-provision an Application Load Balancer and an Auto Scaling group in us-east-1 with the minimum and desired capacity set to 0, and use an automated deployment script to scale out instances to match the primary region during a failover event.

Answer

The correct combination consists of creating an Amazon Aurora Global Database with a secondary cluster configured for Aurora Serverless v2, and pre-provisioning an Application Load Balancer and an Auto Scaling group in the recovery region with a minimum capacity of 0, which is scaled out via automation during failover.
The correct strategy combines database storage-level replication with a Pilot Light compute strategy. Amazon Aurora Global Database uses dedicated infrastructure to replicate data across regions with sub-second latency, satisfying the 2-minute RPO. Operating the secondary Aurora instances as Serverless v2 ensures they only consume minimal capacity when idle, keeping costs low. For the compute layer, pre-provisioning the Application Load Balancer and an Auto Scaling group with a capacity of 0 costs nothing for compute resources during normal operations, but keeps the infrastructure configuration warm. This allows automated scripts to scale the instances up within the 15-minute RTO during a disaster recovery event.

Step-by-Step Solution

1
Analyze RPO constraints
The target RPO is 2 minutes, which requires continuous database replication. Traditional snapshot copies copied every 15 minutes are insufficient.
Choosing a replication strategy with sub-second lag, such as Aurora Global Database, guarantees that data loss is minimized below the 2-minute window.
2
Analyze cost constraints for the database tier
Aurora Serverless v2 instances in the secondary region can scale down to a fraction of an ACU when idle, avoiding the high cost of provisioned instances.
This configuration provides the lowest standby cost while remaining ready to scale up immediately upon failover.
3
Analyze RTO and cost constraints for the compute tier
Setting up an Auto Scaling group with a minimum capacity of 0 in the recovery region ensures that no EC2 costs are incurred during normal operations.
Pre-provisioning the ALB and metadata allows the application to spin up instances quickly via scripts within the 15-minute RTO.

Key Concept

Disaster recovery designs (specifically Pilot Light) utilizing Aurora Global Database and scaled-down compute infrastructure to balance RTO/RPO targets against standby operational costs.
Question 330Question →

A healthcare provider plans to store daily database backup archives in a secondary AWS Region to support their disaster recovery strategy. The database administrator suggests using Amazon S3 Glacier Flexible Retrieval with standard retrieval options, assuming that the archived data can be restored immediately during an unexpected primary site outage. Why is this assumption incorrect?

Show answer & explanation

Answer: Standard retrievals in Amazon S3 Glacier Flexible Retrieval typically take 3 to 5 hours to complete, which introduces significant recovery delays and prevents immediate data access.

Answer

Standard retrievals in Amazon S3 Glacier Flexible Retrieval typically take 3 to 5 hours to complete, which introduces significant recovery delays and prevents immediate data access.
The correct option is correct because standard retrieval requests in Amazon S3 Glacier Flexible Retrieval typically take between 3 to 5 hours to complete. For disaster recovery scenarios that require rapid recovery, this time delay is unacceptable, meaning the assumption of immediate restoration is incorrect.

Step-by-Step Solution

1
Analyze the recovery requirements and the proposed AWS service.
The scenario asks why assuming immediate restore from Amazon S3 Glacier Flexible Retrieval with standard retrieval options is incorrect.
To evaluate the feasibility of the backup and restore solution, we must look at the retrieval latency of the selected storage class.
2
Evaluate the retrieval times of Amazon S3 Glacier Flexible Retrieval.
Amazon S3 Glacier Flexible Retrieval offers three retrieval options: Expedited (1-5 minutes), Standard (3-5 hours), and Bulk (5-12 hours).
Comparing these options reveals that the standard retrieval option does not allow for immediate restoration.
3
Identify the option that correctly states the limitation of the standard retrieval option.
The option stating that standard retrievals typically take 3 to 5 hours is correct.
This delay makes standard retrievals unsuitable for disaster recovery scenarios that require immediate, real-time data access.

Key Concept

Disaster Recovery Storage Retrieval Times
Question 331Question →

A logistics tracking company hosts its web application on Amazon EC2 instances in an Auto Scaling group with an Amazon RDS for PostgreSQL DB instance. The company needs to design a disaster recovery (DR) strategy in a secondary AWS Region. The strategy must achieve a Recovery Point Objective (RPO) of 24 hours and a Recovery Time Objective (RTO) of 12 hours while keeping costs to a minimum.

Which combination of actions will meet these requirements at the lowest cost? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Configure AWS Backup to schedule daily backups of the RDS DB instance and copy them to the secondary Region.; Copy the Amazon Machine Image (AMI) of the application EC2 instances to the secondary Region.

Answer

Configure AWS Backup to schedule daily database backups and copy them to the secondary Region, and copy the application server Amazon Machine Image (AMI) to the secondary Region.
To meet an RPO of 24 hours and RTO of 12 hours at the lowest cost, a Backup and Restore disaster recovery (DR) strategy is ideal. Configuring AWS Backup to schedule daily database backups and copying them to the secondary Region satisfies the 24-hour RPO. Copying the application AMI to the secondary Region ensures that compute resources can be provisioned quickly from the AMI during a disaster event to satisfy the 12-hour RTO. Both of these actions store data at rest and do not run compute or database instances continuously, minimizing costs.

Step-by-Step Solution

1
Identify the recovery requirements (RPO of 24 hours, RTO of 12 hours, minimum cost).
This indicates a Backup and Restore disaster recovery (DR) strategy is appropriate, as it is the most cost-effective and easily fits within a 12-hour window.
Backup and Restore does not require running active compute or database resources in the secondary Region, keeping idle costs at zero.
2
Select the database DR mechanism.
Configure AWS Backup to perform daily database backups and copy them to the secondary Region.
Daily database snapshots meet the 24-hour RPO and can be restored to a new RDS instance within the 12-hour RTO at minimal cost.
3
Select the compute DR mechanism.
Copy the application EC2 AMI to the secondary Region.
Having the AMI available in the secondary Region allows the Auto Scaling group to launch instances from the pre-configured image when failover is initiated, which can be done in minutes.

Key Concept

Backup and Restore is the most cost-effective disaster recovery strategy for scenarios with flexible RTO (e.g., 12-24 hours) and RPO (e.g., 24 hours), as it avoids ongoing compute and active database replica costs in the secondary region.
Question 332Question →

A retail company is launching a new flash sale application where customer transaction events are highly unpredictable and spiky. Each transaction must be processed asynchronously in the exact order it was received to ensure database consistency. Which configurations or services should a solutions architect select? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Amazon SQS FIFO queues to guarantee that messages are processed in the strict order they are received; Message Group IDs to group messages that require sequential processing within the queue

Answer

Amazon SQS FIFO queues should be used to guarantee strict first-in-first-out ordering, and Message Group IDs should be configured to group related messages for sequential processing.
To process customer transaction events in strict order, Amazon SQS FIFO (First-In-First-Out) queues must be used. SQS FIFO queues ensure that the order in which messages are sent and received is strictly preserved. Additionally, Message Group IDs are required in FIFO queues to group messages that belong to a specific session or customer, allowing multiple consumers to process different groups in parallel while maintaining FIFO ordering within each group.

Step-by-Step Solution

1
Analyze the requirement for processing events in the exact order they are received.
Identify that a message queuing service with strict ordering guarantees is required.
Standard SQS queues only provide best-effort ordering, making SQS FIFO queues the correct choice for strict ordering.
2
Determine how to handle related transactions sequentially while allowing parallel processing.
Identify that Message Group IDs should be used to group related messages.
Message Group IDs ensure that messages within the same group are processed in order, while allowing messages in different groups to be processed concurrently.

Key Concept

Decoupling with ordered messaging using SQS FIFO queues and Message Group IDs.
Question 333Question →

A smart home utility company is designing an architecture to ingest telemetry data from millions of smart meters. The telemetry readings from each individual smart meter must be processed in the exact chronological order in which they are generated. Additionally, the architecture must fan out these readings to two separate backend applications: a real-time billing service and an anomaly detection engine. Which combination of actions should the solutions architect recommend to decouple these services while preserving message ordering? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Publish the smart meter telemetry readings to an Amazon SNS FIFO topic, using the unique smart meter identifier as the Message Group ID.; Create two separate Amazon SQS FIFO queues—one for the billing service and one for the anomaly detection engine—and subscribe both queues to the SNS FIFO topic.

Answer

The correct solution is to publish the smart meter telemetry readings to an Amazon SNS FIFO topic using the unique smart meter identifier as the Message Group ID, and to create two separate Amazon SQS FIFO queues subscribed to the SNS FIFO topic.
To achieve both decoupling (fan-out) and strict chronological ordering per device, the architecture must use Amazon SNS FIFO in combination with Amazon SQS FIFO queues. When publishing messages to the SNS FIFO topic, the unique smart meter identifier is designated as the Message Group ID. This ensures that all readings from a single device are kept in sequence. By subscribing separate SQS FIFO queues for the billing service and the anomaly detection engine to the SNS FIFO topic, each consumer application receives an independent copy of the message stream while strictly preserving the FIFO ordering within each device's message group.

Step-by-Step Solution

1
Select a message ingestion and fan-out mechanism that preserves ordering.
Amazon SNS FIFO is selected as it guarantees first-in, first-out ordering and message deduplication while allowing multiple subscribers.
Standard SNS topics do not guarantee message order, which is a key requirement of the scenario.
2
Configure the message grouping strategy.
The unique smart meter identifier is used as the Message Group ID.
This ensures that messages originating from the same physical meter are processed sequentially, while allowing parallel processing across different meters.
3
Decouple downstream consumers without losing the order guarantee.
Two SQS FIFO queues are created and subscribed to the SNS FIFO topic.
SNS FIFO topics can only fan out messages to SQS FIFO queues if end-to-end ordering needs to be maintained for the decoupled consumer services.

Key Concept

End-to-End FIFO Ordering in Decoupled Event-Driven Architectures
Question 334Question →

An energy trading platform hosts its core transaction processing application in the us-east-1 Region. The architecture consists of an Auto Scaling group of Amazon EC2 instances behind an Application Load Balancer (ALB), and a Multi-AZ Amazon RDS for PostgreSQL DB instance. The company needs to design a disaster recovery (DR) solution in the us-west-2 Region. The solution must achieve a Recovery Time Objective (RTO) of 30 minutes and a Recovery Point Objective (RPO) of 5 minutes while minimizing ongoing running costs. Which strategy meets these requirements?

Show answer & explanation

Answer: Deploy an ALB and an Auto Scaling group in the us-west-2 Region with its desired capacity set to 0. Create an RDS for PostgreSQL cross-region read replica in us-west-2. In the event of a disaster, promote the read replica to a standalone DB instance, scale up the Auto Scaling group to its desired capacity, and update the Route 53 DNS records to point to the secondary ALB.

Answer

Deploy an ALB and an Auto Scaling group in the us-west-2 Region with its desired capacity set to 0, create an RDS read replica in the secondary region, promote the replica to standalone during disaster recovery, scale up the Auto Scaling group, and update Route 53 DNS records.
The correct strategy uses an RDS cross-region read replica to satisfy the 5-minute RPO via continuous asynchronous replication. Ongoing costs are minimized by using a Pilot Light strategy, keeping the secondary Auto Scaling group at zero capacity during normal operations. During a disaster, promoting the replica and scaling up the Auto Scaling group allows full system recovery within the 30-minute RTO.

Step-by-Step Solution

1
Set up database replication using an Amazon RDS for PostgreSQL cross-region read replica in the secondary region (us-west-2).
Database changes are replicated asynchronously with sub-second/sub-minute lag, meeting the 5-minute RPO.
Asynchronous cross-region replication is required to achieve the strict RPO without impacting the write latency of the primary database in the us-east-1 Region.
2
Deploy the application load balancer and the Auto Scaling group in the secondary region with the desired capacity set to 0.
The infrastructure is provisioned but runs at zero compute cost during normal operations, meeting the cost optimization requirement.
This implements the Pilot Light recovery pattern, which ensures infrastructure configuration is ready to scale up immediately without incurring continuous EC2 instance costs.
3
Define the disaster recovery failover workflow to promote the read replica to a standalone DB, scale up the Auto Scaling group, and update DNS records to point to the secondary ALB.
The application becomes fully functional in the secondary region within the 30-minute RTO limit.
Promoting an RDS read replica takes only a few minutes, and EC2 instances in the Auto Scaling group can boot and register with the ALB quickly, allowing recovery within the 30-minute target.

Key Concept

Using a cross-region RDS read replica combined with a Pilot Light application tier (zero-capacity Auto Scaling group) allows an architecture to meet low RTO and RPO requirements while keeping idle running costs to a minimum.
Question 335Question →

A company hosts a real-time telemetry processing API on Amazon EC2 instances within an Auto Scaling group (ASG). The instances are located in private subnets and run behind a public-facing Application Load Balancer (ALB). The API is configured to listen on TCP port 8080. The ALB target group has a target port of 8080, but the health check port is explicitly configured to port 80. The network ACL associated with the private subnets allows inbound TCP traffic on port 8080 from the public subnets, and outbound TCP traffic on port 8080 to the public subnets. Currently, all EC2 instances are marked unhealthy by the ALB, causing the ASG to repeatedly terminate and launch new instances. Which two actions must the solutions architect take to resolve this issue and ensure the instances are marked healthy? (Select two.)

Select all that apply

Show answer & explanation

Answer: Modify the target group health check settings to use port 8080 or the traffic port.; Modify the outbound network ACL of the private subnets to allow TCP traffic to the public subnets on ephemeral ports (1024-65535).

Answer

Modify the target group health check settings to use port 8080 or the traffic port, and modify the outbound network ACL of the private subnets to allow TCP traffic to the public subnets on ephemeral ports (1024-65535).
To resolve the health check issues, two corrective configurations must be made. First, the target group's health check port must be changed to port 8080 (or the traffic port) to ensure the Application Load Balancer queries the actual port where the telemetry API is listening. Second, the outbound network ACL of the private subnets must be updated to allow traffic to ephemeral ports (1024-65535). Because network ACLs are stateless, return traffic from the EC2 instances back to the load balancer's dynamically allocated source ports will be dropped unless explicitly permitted by an outbound rule.

Step-by-Step Solution

1
Analyze the target group health check port configuration.
Identify that the health checks are directed to port 80, while the application is bound to port 8080.
Correcting the health check port to match the application port is necessary for the load balancer to receive a valid response.
2
Evaluate the network ACL rules of the private subnets hosting the instances.
Identify that the outbound network ACL only allows TCP port 8080, blocking the return traffic to the load balancer's source ephemeral ports.
Since network ACLs are stateless, return traffic must be explicitly allowed on the destination ports of the response, which are the ephemeral ports used by the ALB.
3
Apply the configuration updates to the health check settings and the outbound network ACL.
The instances successfully pass health checks and are registered as healthy by the Application Load Balancer.
This establishes complete bidirectional network communication required for health check validation.

Key Concept

Application Load Balancer health checks must target the port where the application service is listening, and stateless network ACLs require outbound rules that cover return traffic on ephemeral ports.
Question 336Question →

An IoT-enabled smart parking management system generates vehicle entry and exit events that must be processed in the exact sequence they occur for each vehicle to calculate parking fees accurately. The events must be delivered to both a real-time billing application and an occupancy tracking dashboard. Both downstream applications must receive every event. Which solution meets these requirements while ensuring strict message ordering is preserved for each vehicle?

Show answer & explanation

Answer: Publish the events to an Amazon SNS FIFO topic. Subscribe two Amazon SQS FIFO queues to the topic, one for each downstream application. Use the vehicle ID as the message group ID when publishing the events.

Answer

Publish the events to an Amazon SNS FIFO topic, subscribe two Amazon SQS FIFO queues to the topic, and use the vehicle ID as the message group ID when publishing.
To preserve message ordering end-to-end and deliver every message to multiple downstream consumers (fan-out), both the Amazon SNS topic and the Amazon SQS queues must be configured as FIFO (First-In-First-Out). Publishing events to an SNS FIFO topic with a specific message group ID (the vehicle ID) ensures that all messages for that vehicle are grouped and processed sequentially. The SQS FIFO queues subscribed to the SNS FIFO topic will receive the messages in the exact order they were published, allowing each consumer to process them in sequence.

Step-by-Step Solution

1
Identify the requirement for message ordering and fan-out capability.
The application requires message ordering to be preserved per vehicle ID (ordering requirement) and messages to be delivered to two separate applications (fan-out requirement).
This dictates the choice of messaging services that support both event fan-out and first-in, first-out delivery guarantees.
2
Select the appropriate messaging services to implement a fan-out architecture.
Amazon SNS is selected for fanning out messages, and Amazon SQS is selected to act as the buffer queues for the downstream applications.
SNS allows a single published message to be distributed to multiple subscribers, while SQS queues ensure that messages are buffered and processed asynchronously without losing data.
3
Determine the required queue and topic type for strict ordering.
Select SNS FIFO and SQS FIFO instead of standard types.
Standard SNS and SQS do not guarantee message ordering. To maintain chronological sequence end-to-end, both the SNS topic and the SQS queues must be FIFO.
4
Configure the grouping identifier to order messages per vehicle.
Use the vehicle ID as the Message Group ID (MessageGroupId) when publishing to the SNS FIFO topic.
SQS FIFO and SNS FIFO use the Message Group ID to group messages. Messages within the same group are processed in strict FIFO order, while messages across different groups can be processed in parallel, optimizing performance.

Key Concept

End-to-end first-in, first-out (FIFO) message ordering in fan-out architectures using Amazon SNS FIFO and Amazon SQS FIFO.
Question 337Question →

An online ticketing platform hosts its application on Amazon EC2 instances and its database on an Amazon RDS for MySQL DB instance in the us-east-1 Region. The platform needs to implement a disaster recovery (DR) strategy in the us-west-2 Region. The strategy must support a Recovery Point Objective (RPO) of 5 minutes and a Recovery Time Objective (RTO) of 30 minutes. Which combination of actions should a solutions architect recommend 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-west-2 Region.; Configure Amazon Route 53 with a failover routing policy and associate it with health checks to route traffic to the secondary Region.

Answer

Create a cross-region read replica of the RDS DB instance in the secondary Region, and configure Amazon Route 53 with a failover routing policy and health checks to route traffic to the secondary Region.
Creating a cross-region read replica of the database satisfies the 5-minute RPO requirement because data is replicated asynchronously to the secondary Region. Promoting the replica to a primary instance takes under 30 minutes. Concurrently, Route 53 failover routing with health checks detects primary region outages and automatically redirects client application traffic to the secondary Region, keeping overall RTO under 30 minutes.

Step-by-Step Solution

1
Address the 5-minute RPO constraint for database replication.
Create a cross-region read replica of the RDS MySQL DB instance in the target DR Region.
This establishes asynchronous replication across Regions, keeping data lag down to seconds or minutes and meeting the RPO.
2
Address the 30-minute RTO constraint for traffic failover.
Configure Route 53 with a failover routing policy and configure active health checks on the primary endpoints.
Health checks monitor endpoint status and failover routing redirects traffic to the DR Region within minutes of a detected failure.

Key Concept

Combining cross-region database replication with Route 53 failover routing to meet low RTO and RPO disaster recovery objectives.
Question 338Question →

A financial services company is migrating a legacy payment settlement system to AWS. The system must process account withdrawal requests sequentially on a per-account basis to prevent overdrafts. The transaction volume is highly spiky and can reach up to 80008{}000 requests per second. The company wants to design a decoupled, resilient, and serverless messaging architecture that guarantees ordering within each account while maximizing throughput and minimizing operational overhead.

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 SQS FIFO queue and enable high-throughput mode for the queue.; Publish the withdrawal events using the unique account number as the Message Group ID.

Answer

The correct solution is to create an Amazon SQS FIFO queue with high-throughput mode enabled, and publish the withdrawal events using the unique account number as the Message Group ID.
To satisfy both ordering and scale requirements, the architecture must use Amazon SQS FIFO with high-throughput mode enabled. Using the account number as the Message Group ID ensures that messages for the same account are processed in order, while messages for different accounts can be processed concurrently by multiple consumers. This design provides both the necessary ordering guarantees and the scalability to support 8,000 transactions per second.

Step-by-Step Solution

1
Select a message queue service that guarantees first-in, first-out (FIFO) order.
Amazon SQS FIFO queue is selected because SQS Standard queues cannot guarantee message ordering.
Sequential processing on a per-account basis is a hard requirement to prevent overdrafts.
2
Enable high-throughput mode on the SQS FIFO queue.
The queue can support throughput scales of up to 80008{}000 transactions per second or more.
Normal SQS FIFO queues are limited to 300 transactions per second (or 3,000 with batching) by default, which is insufficient for the peak load of 8,000 requests per second.
3
Configure the message grouping strategy using a granular partition key.
The unique account number is used as the Message Group ID for each SQS FIFO message.
Using the account number ensures strict ordering within each individual account while allowing parallel processing across different accounts to meet the high-throughput demands.

Key Concept

Decoupling event-driven workloads with Amazon SQS FIFO high-throughput mode and Message Group IDs.
Question 339Question →

An online learning platform uses a web application to manage student course enrollments. The system must decouple the front-end enrollment portal from the back-end database processing service. To ensure fair registration for courses with limited capacity, enrollment requests must be processed in the exact sequence they are submitted. Which messaging service configuration should a solutions architect recommend to decouple these components while maintaining the correct message sequence?

Show answer & explanation

Answer: An Amazon SQS FIFO queue

Answer

An Amazon SQS FIFO queue
An Amazon SQS FIFO queue is the correct solution because it successfully decouples the application tiers and guarantees that messages are processed in the exact order they are sent, satisfying the requirement for sequential enrollment processing.

Step-by-Step Solution

1
Analyze the requirement for decoupling the web portal and the database service.
Identify that a message queue or event bus is needed to decouple the frontend from the backend.
Decoupling ensures the front-end application remains responsive even if the back-end database has processing delays.
2
Evaluate the ordering constraint for the enrollment requests.
Identify that the solution must guarantee first-in, first-out (FIFO) processing to ensure fair registration.
Standard message queues do not guarantee strict message ordering.
3
Select the AWS service that provides both decoupling and strict ordering.
Determine that Amazon SQS FIFO (First-In-First-Out) queues meet both criteria.
SQS FIFO queues guarantee that the order in which messages are sent and received is strictly preserved.

Key Concept

Using Amazon SQS FIFO queues to decouple application components while maintaining message ordering.
Estimated Time:45s
Question 340Question →

A company hosts a REST API on Amazon EC2 instances in an Auto Scaling group (ASG) behind an Application Load Balancer (ALB). The API service is configured to bind and listen on custom TCP port 5001. The EC2 instances are deployed in private subnets, and their security group permits inbound traffic on port 5001 from the ALB's security group. After a scale-out event, the newly launched instances are repeatedly marked as unhealthy by the ALB target group and are subsequently terminated by the ASG. An investigation reveals that the ALB target group health check is set to the default port, and the private subnet Network ACLs only have explicit rules allowing inbound TCP port 5001 and outbound TCP port 5001. Which two configuration changes must the solutions architect implement to resolve the health check failures and ensure the instances remain in service? (Select two.)

Select all that apply

Show answer & explanation

Answer: Modify the target group's health check port setting to use port 5001.; Add an outbound rule to the private subnet Network ACL to allow traffic to ephemeral ports (1024−655351024-65535).

Answer

Modify the target group's health check port setting to use port 5001, and add an outbound rule to the private subnet Network ACL to allow traffic to ephemeral ports (1024−655351024-65535).
To resolve the issue, the Solutions Architect must address two distinct configuration gaps. First, the Application Load Balancer target group must be modified to perform health checks on the custom port (5001) instead of the default port (80), ensuring it aligns with the API application port. Second, because Network ACLs are stateless, return traffic from the instances to the ALB must be explicitly allowed. Since the ALB initiates connections to the instances, the response traffic is sent back to the ALB's ephemeral client ports, requiring an outbound Network ACL rule to allow the ephemeral port range (1024−655351024-65535).

Step-by-Step Solution

1
Identify the cause of target group health check failure.
The target group defaults to port 80 for health checks, whereas the API listens on port 5001. Modifying the target group's health check configuration to target port 5001 is required.
Health checks must target the port where the application actually listens, otherwise the load balancer will receive connection timeouts or connection refused errors.
2
Analyze network traffic flow through the subnet Network ACLs.
The Network ACL currently only allows outbound traffic on TCP port 5001. Because Network ACLs are stateless, the return traffic from the instances back to the load balancer (which uses ephemeral ports 1024−655351024-65535) is blocked.
To allow communication, the Network ACL must allow inbound request traffic on port 5001 and outbound return traffic on the ephemeral port range.

Key Concept

ELB health checks require target group configuration alignment with application ports, and stateless network components like Network ACLs require explicit configuration of return traffic to ephemeral ports.
Estimated Time:2m 0s
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