<strong>A startup company has a new feature which is used to track the customers’ feedback on its main website. On the website, there are product introductions and also customers are able to purchase the products and get them delivered. The development team has utilized Elastic Beanstalk to deploy the new feedback system. One developer just made a big change to the survey format and deployed the feature to a totally new Elastic Beanstalk Environment. Then he used the “Swap URL” function to switch to the new one. After monitoring the site for a day, by tracing the logs, the developer found that there were still few cases that old survey format was used even after about 12 hours. Which below explanation is correct?</strong>

Answer options:

A.There is a possibility that the Elastic BeanStalk environment is still using the code related to the old survery format. Rollback the Elastic Beanstalk environment and deploy it newly
B."Swap URL" is a feature of Route53 to change the DNS settings of website. There is a possibility that the CNAME used is wrong and therefore the old survey format still exists. ROute53 configurations needs to be checked and modified
C."Swap URL" is a feature of Route53 to change the DNS settings of website. There is a possibility that the TTL settings for the website is too high and therefore the old survey format still exists. ROute53 configurations needs to be checked and modified
D."Swap URL" is a feature of Elastic Beanstalk to change the DNS settings of website. There is a possibility that there is an issue with the TTL settings and the DNS clients does not comply with the TTL settings

Option D is Correct:
After Elastic Beanstalk completes the swap operation, users should verify that the new environment responds when they try to connect to the old environment URL. However, do not terminate your old environment until the DNS changes have been propagated.
Besides, DNS clients exist at various levels, and not all of them obey TTL rules. If users are dealing with mobile, particularly internationally, this is even worse. Using DNS for blue/green deployments means the switch over will not be clean, and both sets will need to be live for a much longer period of time than they should be, costing you money. Details please refer to
https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/using-features.CNAMESwap.html
https://minops.com/blog/2015/02/the-dos-and-donts-of-bluegreen-deployment/
Option A is incorrect:DNS TTL issue should be suspected in this case for Swap URL and if wrong code branch was deployed, there should not be just few cases that were using wrong survey formats.
Option B is incorrect:if wrong CNAME was used, all cases should be wrong however there are only few cases that were wrong.
Option C is incorrect:TTL setting may be an issue however it should affect all users.
Besides, Swap URL has modified CNAME rather than Alias record.