Answer - B and C.
This is mentioned in an AWS whitepaper.
You can shift traffic all at once, or you can do a weighted distribution.
With Amazon Route 53, you can define a percentage of traffic to go to the green environment and gradually update the weights until the green environment carries the full production traffic.
A weighted distribution provides the ability to perform canary analysis where a small percentage of production traffic is introduced to a new environment.
It also allows the green environment to scale out to support the full production load if you're using Elastic Load Balancing, for example.
Elastic Load Balancing automatically scales its request-handling capacity to meet the inbound application traffic.
Option A is invalid since this is used for failover purposes.
Option D is invalid since you should not deploy your applications using just a single AZ.
For more information on Blue Green deployments, please refer to the below URL-
https://d1.awsstatic.com/whitepapers/AWS_Blue_Green_Deployments.pdf
Blue-green deployment is a technique for releasing new versions of software by creating two identical environments, one blue (active) and one green (inactive). The new version of the application is deployed in the inactive environment (green), and once it is tested and validated, traffic is redirected from the old version (blue) to the new version (green).
To achieve blue-green deployment in AWS, you can use the following two methods:
- Use Route 53 with the weighted routing policy:
Route 53 is Amazon's DNS web service that allows you to route traffic to your application based on various routing policies. Weighted routing policy allows you to distribute traffic between two or more identical resources based on a predefined weight.
In a blue-green deployment scenario, you can configure two identical sets of resources (e.g., EC2 instances, load balancers, or Auto Scaling groups), one set for the blue environment and another for the green environment. You can then use Route 53 with a weighted routing policy to route a certain percentage of traffic to each environment. For example, you can route 90% of the traffic to the blue environment and 10% to the green environment initially. After you validate the green environment, you can gradually increase the percentage of traffic routed to it until all traffic is directed to the green environment.
- Ensure that the application is placed behind an Elastic Load Balancer (ELB):
An Elastic Load Balancer (ELB) automatically distributes incoming traffic across multiple EC2 instances. ELB can be used to create blue-green deployments by configuring it to distribute traffic between two identical environments.
In this method, you can configure two identical sets of EC2 instances, one set for the blue environment and another for the green environment, and place them behind an ELB. You can then route all traffic to the ELB. Once the green environment is tested and validated, you can switch the traffic to the green environment by updating the ELB configuration.
Therefore, the correct answers to this question are B. Use Route 53 with the weighted routing policy and C. Ensure that the application is placed behind an ELB.
