AWS Certified Developer – Associate (DVA-C02) — Question 372

A developer wants the ability to roll back to a previous version of an AWS Lambda function in the event of errors caused by a new deployment.

How can the developer achieve this with MINIMAL impact on users?

Answer options

• A. Change the application to use an alias that points to the current version. Deploy the new version of the code. Update the alias to use the newly deployed version. If too many errors are encountered, point the alias back to the previous version.
• B. Change the application to use an alias that points to the current version. Deploy the new version of the code. Update the alias to direct 10% of users to the newly deployed version. If too many errors are encountered, send 100% of traffic to the previous version.
• C. Do not make any changes to the application. Deploy the new version of the code. If too many errors are encountered, point the application back to the previous version using the version number in the Amazon Resource Name (ARN).
• D. Create three aliases: new, existing, and router. Point the existing alias to the current version. Have the router alias direct 100% of users to the existing alias. Update the application to use the router alias. Deploy the new version of the code. Point the new alias to this version. Update the router alias to direct 10% of users to the new alias. If too many errors are encountered, send 100% of traffic to the existing alias.

Correct answer: B

Explanation

Using AWS Lambda routing configurations on an alias allows for canary deployments, where only a small percentage of traffic (such as 10%) is exposed to the new version. This minimizes user impact because if errors are detected, the developer can instantly shift 100% of the traffic back to the stable version. Other options either expose all users to the new code immediately or introduce redundant and overly complex alias configurations.