Design Resilient Architectures

382 questions

All types382 Multiple choice195 Multiple select187

A food delivery platform is designing a resilient, event-driven system to process order status updates (such as 'Order Placed', 'Out for Delivery', and 'Delivered'). The order status updates for each individual order must be processed in the exact chronological sequence they occur to ensure the customer dashboard displays accurate updates. A marketing analytics service also needs to receive these updates to track daily delivery metrics, but ordering is not critical for this service. Which combination of actions should a solutions architect take to meet these requirements with the least operational overhead? (Select TWO.)

Select all that apply

Create an Amazon SNS FIFO topic to receive the updates, and use the order ID as the message group ID.

Create an Amazon SQS FIFO queue for the customer dashboard service, and subscribe it to the SNS FIFO topic.

Create a standard Amazon SQS queue for the customer dashboard service, and subscribe it to the SNS FIFO topic.

Create a standard Amazon SNS topic to receive the updates, and subscribe an Amazon SQS FIFO queue for the customer dashboard service to it.

Create a standard Amazon SQS queue for the customer dashboard service, and configure the service to query the queue using client-side ordering logic.

Show answer & explanation

Answer: Create an Amazon SNS FIFO topic to receive the updates, and use the order ID as the message group ID.; Create an Amazon SQS FIFO queue for the customer dashboard service, and subscribe it to the SNS FIFO topic.

Answer

To decouple the systems and maintain chronological ordering, create an Amazon SNS FIFO topic using the order ID as the message group ID, and subscribe an Amazon SQS FIFO queue for the customer dashboard service to the SNS FIFO topic.

To satisfy the strict chronological ordering requirement with minimal operational overhead, the solution must implement FIFO messaging end-to-end. Creating an Amazon SNS FIFO topic and specifying the order ID as the message group ID ensures that events for a specific order are partitioned and ordered correctly. Subscribing an Amazon SQS FIFO queue to this SNS FIFO topic ensures that the customer dashboard service consumes these updates in order. The marketing analytics service (which does not require ordering) can also subscribe to the SNS FIFO topic using its own SQS FIFO queue, since SNS FIFO only supports SQS FIFO subscriptions.

Step-by-Step Solution

Analyze the ordering requirement.

Order status updates for individual orders must be processed chronologically, requiring first-in, first-out (FIFO) delivery semantics.

Standard messaging services do not guarantee strict ordering, so FIFO-enabled services are required.

Select the appropriate fan-out and messaging decoupling components.

An Amazon SNS FIFO topic is selected for event fan-out, and an Amazon SQS FIFO queue is selected for the order-sensitive customer dashboard subscriber.

SNS FIFO topics support SQS FIFO queues as subscribers to guarantee end-to-end message ordering and deduplication.

Configure the message grouping strategy.

The order ID is specified as the message group ID for the SNS FIFO topic.

The message group ID determines the ordering scope, ensuring updates for the same order are processed sequentially without impacting other concurrent orders.

Key Concept

Preserving message ordering end-to-end in event-driven systems using Amazon SNS FIFO and Amazon SQS FIFO integration.

Question 382Question →

A flight booking aggregator application hosts its primary infrastructure 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 Multi-AZ Amazon RDS for MySQL database. The company needs to design a cross-region disaster recovery (DR) plan to a secondary AWS region. The DR solution must achieve a Recovery Time Objective (RTO) of $4$ hours and a Recovery Point Objective (RPO) of $15$ minutes while minimizing ongoing infrastructure running costs. Which solution meets these requirements?

Configure the RDS database with Multi-AZ deployment and use an Auto Scaling group across multiple Availability Zones in the primary region. Configure Amazon Route 53 latency routing to automatically direct traffic.

Configure a cross-region read replica of the RDS database in the secondary region. Store pre-baked AMIs of the EC2 instances in both regions. In the event of a disaster, promote the read replica to a standalone database and launch the EC2 instances in the secondary region using the AMIs.

Export database backups every

15

minutes to Amazon S3 Glacier Flexible Retrieval and configure S3 Cross-Region Replication to copy the backups to the secondary region. In the event of a disaster, retrieve the backups from Glacier to restore the database and launch the EC2 instances.

Deploy a scaled-down active version of the application stack, including a running, smaller RDS database instance and an active EC2 instance in the secondary region, and scale up the environment during a failover event.

Show answer & explanation

Answer: Configure a cross-region read replica of the RDS database in the secondary region. Store pre-baked AMIs of the EC2 instances in both regions. In the event of a disaster, promote the read replica to a standalone database and launch the EC2 instances in the secondary region using the AMIs.

Answer

The correct solution configures a cross-region read replica of the RDS database to meet the RPO and stores pre-baked AMIs to launch EC2 instances in the secondary region during a disaster to meet the RTO while minimizing ongoing costs.

The correct solution uses a Pilot Light disaster recovery strategy. Creating a cross-region read replica of the Amazon RDS database ensures that data is continuously replicated asynchronously to the secondary region, which achieves a Recovery Point Objective (RPO) of minutes, well within the

15

-minute limit. Storing pre-baked AMIs of the EC2 instances allows them to be launched quickly during a failover event, which easily meets the Recovery Time Objective (RTO) of

4

hours. Because the EC2 instances are not running in the secondary region until a disaster occurs, this approach minimizes ongoing infrastructure running costs.

Step-by-Step Solution

Analyze the disaster recovery constraints: RTO must be under

4

hours, RPO must be under

15

minutes, and ongoing running costs must be minimized.

The RPO constraint requires a data replication mechanism that lag is less than

15

minutes. The RTO constraint allows up to

4

hours to bring the system online. Cost minimization suggests keeping compute resources offline (Pilot Light) rather than scaled down and active (Warm Standby).

Identifying the target recovery objectives determines the boundary between acceptable DR strategies (Backup & Restore, Pilot Light, Warm Standby, Active-Active).

Evaluate database replication options for Amazon RDS for MySQL.

A cross-region read replica replicates data asynchronously, typically within seconds or minutes, satisfying the

15

-minute RPO. Restoring from S3 Glacier backups fails the RTO due to retrieval times.

Ensuring the selected replication technology satisfies the RPO requirement.

Evaluate the compute environment configuration for the recovery region.

Storing pre-baked AMIs and launching EC2 instances in the recovery region only when a disaster occurs keeps ongoing compute costs at zero, meeting the cost optimization goal while easily completing the failover within

4

hours.

Selecting the most cost-efficient compute strategy that still satisfies the recovery timeline.

Key Concept

AWS Disaster Recovery Strategies: Pilot Light vs. Warm Standby

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Design Resilient Architectures

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Step-by-Step Solution

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Common Mistakes

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Step-by-Step Solution

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Common Mistakes