A and D is correct. But Route 53 haves a feature DNS failover when instances down so we dont need use Cloudwatch and lambda to trigger -> A correct

They are not asking for automatic failover, they want to "ensure the application can (!) be made available in another AWS Region with minimal downtime". This works with C; they would just execute the template and it would be available in short time. A would create a DR environment that IS already available, which is not what the question asks for. D is like A, just abusing Lambda to update the DNS record (which doesn't make sense). B would create a separate, empty database

With the LEAST amount of downtime = A Cost effective = C , but risky some of EC2 types/capacity not available in Region at the time, when need to switch to DR

There are 2 parts. DB and application. Dynamo DB recovery in another region is not possible without global table so option B is out. A will make the infra available in 2 regions which is not required. The question is about DR, not scaling. D Use Lambda to modify R53 to point to new region. This is going to cause delays but is possible and it will also be running a scaled EC2 instances in passive region. C Make a CF template which can launch the infra when needed. DB is global table so it will be available.

AWS CloudFormation Template: Use CloudFormation to define the infrastructure components (EC2 instances, load balancer, etc.) in a template. This allows for consistent and repeatable infrastructure deployment. EC2 Instances and Load Balancer: Launch the EC2 instances and load balancer in the disaster recovery (DR) Region using the CloudFormation template. This enables the deployment of the application in the DR Region when needed. DynamoDB Global Table: Configure the DynamoDB table as a global table. DynamoDB Global Tables provide automatic multi-region, multi-master replication, ensuring that the data is available in both the primary and DR Regions. DNS Failover: Configure DNS failover to point to the new DR Region's load balancer. This allows for seamless failover of traffic to the DR Region when needed. Option A is close, but it introduces an Auto Scaling group in the disaster recovery Region, which might introduce unnecessary complexity and potential scaling delays. Option D introduces a Lambda function triggered by CloudWatch alarms, which might add latency and complexity compared to the more direct approach in Option C.

Assuming theyre using Route53 as a DNS then A https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/dns-failover.html

Only B and C take care of EC2 instants. But since B does not take care of Data in the Dynamo DB, C is the only correct Answer.

Route 53 haves a feature DNS failover when instances down

C is the best choice here

I think CloudFormation is easier than manual provision of Auto Scaling group and load balancer in DR region.

Creating Auto Scaling group and load balancer in DR region allows fast launch of capacity when needed. Configuring DynamoDB as a global table provides continuous data replication. Using DNS failover via Route 53 to point to the DR region's load balancer enables rapid traffic shifting.

Both Option A and Option D include the necessary steps of setting up an Auto Scaling group and load balancer in the disaster recovery Region, configuring the DynamoDB table as a global table, and updating DNS records. However, Option D provides a more detailed approach by explicitly mentioning the use of an Amazon CloudWatch alarm and AWS Lambda function to automate the DNS update process. By leveraging an Amazon CloudWatch alarm, Option D allows for an automated failover mechanism. When triggered, the CloudWatch alarm can execute an AWS Lambda function, which in turn can update the DNS records in Amazon Route 53 to redirect traffic to the disaster recovery load balancer in the new Region. This automation helps reduce the potential for human error and further minimizes downtime. Answer is D

The company wants to ensure the application 'CAN' be made available in another AWS Region with minimal downtime. Meaning they want to be able to launch infra on need basis. Best answer is C.

I feel it is A Configure DNS failover: Use DNS failover to point the application's DNS record to the load balancer in the disaster recovery Region. DNS failover allows you to route traffic to the disaster recovery Region in case of a failure in the primary Region.

C suits best

AがDNS フェイルオーバー

A By configuring the DynamoDB table as a global table, you can replicate the table data across multiple AWS Regions, including the primary Region and the disaster recovery Region. This ensures that data is available in both Regions and can be seamlessly accessed during a failover event.