This solution is operationally efficient and leverages AWS services to provide notifications when the

Lambda function is not invoked, indicating that the file did not arrive.

Steps:

Create a CloudWatch Alarm:

Open the Amazon CloudWatch console.

In the navigation pane, choose "Alarms" and then "Create Alarm".

Select Lambda Metrics:

Choose "Select metric" and then navigate to "AWS Lambda" metrics.

Select the Lambda function that processes the S3 files.

Choose the "Invocations" metric.

Configure the Alarm:

Set the period to 1 hour.

Define the threshold condition to trigger when the Invocations metric is zero.

Under "Additional configuration", configure the alarm to treat missing data as "breaching".

Set Alarm Actions:

Configure the alarm action to send a notification to an Amazon SNS topic.

Create an SNS topic if one does not exist, and subscribe the application team to this topic.

Testing and Verification:

Ensure that the alarm triggers correctly by simulating a missing file scenario and confirming that the

notification is sent to the SNS topic.

This approach uses CloudWatch to monitor the invocation frequency of the Lambda function,

ensuring that the application team is notified whenever the expected file does not arrive within the

specified timeframe.

Reference:

Amazon CloudWatch Alarms

Monitoring Lambda Functions

Amazon SNS Notifications