A company deploys the same CloudFormation template to separate stacks for each environment. The developer must notify the QA team when new deployments occur in the final preproduction environment. What is the best way to provide those notifications?

The most straightforward and efficient solution is to use Amazon SNS directly with CloudFormation. CloudFormation has a built-in feature to publish stack events to an SNS topic. By creating an SNS topic, subscribing the QA team to it, and then specifying this SNS topic in the NotificationARNs parameter when creating or updating the preproduction CloudFormation stack, all stack events (including deployment completion) will be sent to the topic, notifying the QA team. The Lambda function with EventBridge rule is a valid approach but adds unnecessary complexity for a simple notification task that CloudFormation can handle natively. CloudWatch alarms are for monitoring metrics and thresholds, not for direct event notifications from CloudFormation deployments. A Lambda function with an event source mapping from CloudFormation is not a standard or direct integration method for CloudFormation stack events; CloudFormation's direct SNS integration is preferred.