I have created a Python lambda function which gets executed as soon as a .zip file lands in a particular folder in an s3 bucket. Now there may be a situation where there is no file uploaded to the S3 within in a certain time period (for example 10 AM morning). How to get an alert for tracking no file arrival?
You may use cloudwatch alarms. You can set an alarm  when no event (e.g. lambda execution) is present for metrics.
It has only basic options to configure, but imho it's the simplest solution
Alert for no file uploaded to S3 within a particular time