AWS Budgets allows you to create budgets for your AWS accounts and set alerts when usage exceeds a certain threshold. By creating a budget for each account, specifying the period as monthly and the scope as EC2 instances, you can effectively track the EC2 usage for each account and be notified when a threshold is exceeded. This solution is the most cost-effective option as it does not require additional resources such as Amazon Athena or Amazon EventBridge.

AWS Budgets allows you to create budgets for your AWS accounts and set alerts when usage exceeds a certain threshold. By creating a budget for each account, specifying the period as monthly and the scope as EC2 instances, you can effectively track the EC2 usage for each account and be notified when a threshold is exceeded. This solution is the most cost-effective option as it does not require additional resources such as Amazon Athena or Amazon EventBridge.

Option A and Option B suggest using Cost Explorer to create reports and send notifications. While Cost Explorer is useful for analyzing costs, it does not provide the real-time alerting capability that AWS Budgets offers. Option D suggests using AWS Cost and Usage Reports integrated with Amazon Athena and Amazon EventBridge, which can be a more complex and potentially costlier solution compared to AWS Budgets for this specific use case. It's also more suitable for fine-grained, custom analytics rather than straightforward threshold-based alerts.

AWS Budgets was designed to handle this scenario.

Use AWS Budgets to create a cost budget for each account. Set the period to monthly. Set the scope to EC2 instances. Set an alert threshold for the budget. Configure an Amazon Simple Notification Service (Amazon SNS) topic to receive a notification when a threshold is exceeded.

By creating a cost budget for each account, specifying the period as monthly and scoping it to EC2, you can track and monitor the costs associated with EC2 specifically. Set an alert threshold in the budget, which will trigger a notification when the specified threshold is exceeded. Configure an SNS to receive the notification, which can be subscribed to by the company to receive immediate alerts. A and B are not the most cost-effective solutions as they involve using Cost Explorer to create reports, which may not provide real-time notifications when the threshold is exceeded. Additionally, A. suggests using a daily report, while B. suggests using a monthly report, which may not provide the desired level of granularity for immediate notifications. D involves using Cost and Usage Reports with Athena and EventBridge. This solution provides more flexibility and data analysis capabilities, it is more complex and may incur additional costs for using Athena and generating hourly reports.

I go with D. It says "as soon as", "daily" reports seems to be a bit longer time frame to wait in my opinion.

C: AWS Budgets allows you to set a budget for costs and usage for your accounts and you can set alerts when the budget threshold is exceeded in real-time which meets the requirement. Why not B: B would be the most cost-effective if the requirements didn't ask for real-time notification. You would not incur additional costs for the daily or monthly reports and the notifications. But doesn't provide real-time alerts.

Agree...C

Answer is C

https://aws.amazon.com/getting-started/hands-on/control-your-costs-free-tier-budgets/

AWS budget IMO, it's done for it