Question 36

Domain 2: Design for New Solutions

A company needs to implement a disaster recovery (DR) plan for a web application. The application runs in a single AWS Region. The application uses microservices that run in containers. The containers are hosted on AWS Fargate in Amazon Elastic Container Service (Amazon ECS). The application has an Amazon RDS for MYSQL DB instance as its data layer and uses Amazon Route 53 for DNS resolution. An Amazon CloudWatch alarm invokes an Amazon EventBridge rule if the application experiences a failure. A solutions architect must design a DR solution to provide application recovery to a separate Region. The solution must minimize the time that is necessary to recover from a failure. Which solution will meet these requirements?

A. Set up a second ECS cluster and ECS service on Fargate in the separate Region. Create an AWS Lambda function to perform the following actions: take asnapshot of the ROS DB instance. copy the snapshot to the separate Region. create a new RDS DB instance frorn the snapshot, and update Route 53 to route traffic to the second ECS cluster. Update the EventBridge rule to add a target that will invoke the Lambda function. B. Create an AWS Lambda function that creates a second ECS cluster and ECS service in the separate Region. Configure the Lambda function to perform thefollowing actions: take a snapshot of thQRDS DB instance, copy the snapshot to the separate Region. create a new RDS DB instance from the snapshot.and update Route 53 to route traffic to the second ECS cluster. Update the EventBridge rule to add a target that will invoke the Lambda function. C. Set up a second ECS cluster and ECS service on Fargate in the separate Region. Create a cross-Region read replica of the RDS DB instance in theseparate Region. Create an AWS Lambda function to prornote the read replica to the primary database. Configure the Lambda function to update Route 53to route traffic to the second ECS cluster. Update the EventBridge rule to add a target that will invoke the Lambda function. D. Set up a second ECS cluster and ECS service on Fargate in the separate Region. Take a snapshot of the ROS DB instance. Convert the snapshot to anAmazon DynamoDB global table. Create an AWS Lambda function to update Route 53 to route traffic to the second ECS cluster Update the EventBridgerule to add a target that will invoke the Lambda function.

Correct answer: C

Explanation

This design minimizes recovery time by keeping a warm standby in the other Region: a second ECS/Fargate service is already deployed, and a cross-Region read replica can be promoted quickly. EventBridge can trigger Lambda on failure, and Lambda can “promote the read replica” and “update Route 53 to route traffic” for automated failover.

Why each option is right or wrong

Snapshot copy and restore rebuild the database after failure; they are slower than replica promotion.

B. Create an AWS Lambda function that creates a second ECS cluster and ECS service in the separate Region. Configure the Lambda function to perform thefollowing actions: take a snapshot of thQRDS DB instance, copy the snapshot to the separate Region. create a new RDS DB instance from the snapshot.and update Route 53 to route traffic to the second ECS cluster. Update the EventBridge rule to add a target that will invoke the Lambda function.

Lambda can automate failover, but creating the standby cluster only during failure adds recovery delay.

C. Set up a second ECS cluster and ECS service on Fargate in the separate Region. Create a cross-Region read replica of the RDS DB instance in theseparate Region. Create an AWS Lambda function to prornote the read replica to the primary database. Configure the Lambda function to update Route 53to route traffic to the second ECS cluster. Update the EventBridge rule to add a target that will invoke the Lambda function.

AWS ECS on Fargate is a regional service, so a separate Region must already have its own ECS cluster/service deployed to avoid the delay of provisioning compute during an outage. For the database, Amazon RDS cross-Region read replicas can be promoted to standalone primaries in the failover Region, and Route 53 can be updated by automation to shift DNS there; tying the existing EventBridge failure event to a Lambda target gives near-immediate failover without waiting for manual intervention.

D. Set up a second ECS cluster and ECS service on Fargate in the separate Region. Take a snapshot of the ROS DB instance. Convert the snapshot to anAmazon DynamoDB global table. Create an AWS Lambda function to update Route 53 to route traffic to the second ECS cluster Update the EventBridgerule to add a target that will invoke the Lambda function.

DynamoDB global tables are a different database platform and do not convert from an RDS snapshot.

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