Question

A SysOps administrator must ensure that whenever an EC2 instance in the development account transitions to the 'running' state, an automated process applies a mandatory cost-allocation tag if the tag is missing. The solution should be fully event-driven, require no polling, and incur minimal ongoing operational overhead. Which approach best meets these requirements?

Accepted Answer

Create an EventBridge rule that matches the EC2 Instance State-change Notification event for 'running' and targets a Lambda function that checks for and adds the missing tag.

Answer

Configure a CloudWatch alarm on the EC2 StatusCheckFailed metric to trigger a Lambda function that tags the instance.

Answer

Schedule a Lambda function with an EventBridge cron rule to run every 5 minutes, scan all running instances, and tag any that are missing the tag.

Answer

Enable AWS Config with a managed rule for required tags and rely on its periodic evaluation to add the missing tag automatically.