What is the MOST operationally efficient solution that meets these requirements?
Add an S3 Lifecycle rule on the S3 bucket with a scope that is limited to objects that were created in the last hour. Configure another S3 event notification to be invoked by the lifecycle transition when the number of objects transitioned is zero. Publish a message to an Amazon Simple Notification Service (Amazon SNS) topic to notify the application team.
Configure another S3 event notification to invoke a Lambda function that posts a message to an Amazon Simple Queue Service (Amazon SQS) queue. Create an Amazon CloudWatch alarm to publish a message to an Amazon Simple Notification Service (Amazon SNS) topic to notify the application team when the ApproximateAgeOfOldestMessage metric of the queue is greater than 1 hour.
Create an Amazon CloudWatch alarm to publish a message to an Amazon Simple Notification Service (Amazon SNS) topic to alert the application team when the Invocations metric of the Lambda function is zero for an hour. Configure the alarm to treat missing data as breaching.
Create a new Lambda function to get the timestamp of the newest file in the S3 bucket. If the timestamp is more than 1 hour ago, publish a message to an Amazon Simple Notification Service (Amazon SNS) topic to notify the application team. Create an Amazon EventBridge (Amazon CloudWatch Events) rule to invoke the new function hourly.
Explanations:
Adding an S3 Lifecycle rule does not directly relate to the timely arrival of files. Lifecycle rules are designed for managing the lifecycle of objects rather than detecting the absence of new files. The approach of relying on a lifecycle transition to trigger notifications is not efficient or appropriate for the requirement of detecting missing files hourly.
While using SQS to track the arrival of files could theoretically work, it is not the most efficient way to meet the requirement. The additional complexity of managing SQS, along with the need for monitoring theApproximateAgeOfOldestMessagemetric, makes this solution less direct and more cumbersome compared to other options.
Monitoring theInvocationsmetric of the Lambda function is a direct and effective way to ensure that the file processing is happening as expected. If the Lambda function is not invoked for an hour, this indicates that no new files have arrived. The use of CloudWatch alarms to publish notifications is an operationally efficient method for the application team to be alerted of the issue.
While this option could work, it involves creating a new Lambda function that checks for the timestamp of the latest file, which adds unnecessary complexity and operational overhead. The requirement is to get notified of missing files, and using CloudWatch metrics for the existing Lambda function is a simpler and more efficient solution.
I rate that the answer is:
Create an Amazon CloudWatch alarm to publish a message to an Amazon Simple Notification Service (Amazon SNS) topic to alert the application team when the Invocations metric of the Lambda function is zero for an hour. Configure the alarm to treat missing data as breaching.