With S3 you don't even need lambda to do something like this
S3 has some setting where you can log activity on a bucket into another bucket
But that setting allows you to set the destination bucket to be the same bucket that you're monitoring. So ~30s after something happens on the monitored bucket, S3 writes a log into the same bucket. And then that activity triggers the logging again. So every ~30-60s, forever, there's a little log written into the bucket.
It takes a while to add up to something noticeable if your monthly AWS bill is already a few digits long. It's super fun to sift through the bucket a few months later when you're trying to figure out if there's any real data in the bucket or just endless logs.
S3 has some setting where you can log activity on a bucket into another bucket
But that setting allows you to set the destination bucket to be the same bucket that you're monitoring. So ~30s after something happens on the monitored bucket, S3 writes a log into the same bucket. And then that activity triggers the logging again. So every ~30-60s, forever, there's a little log written into the bucket.
It takes a while to add up to something noticeable if your monthly AWS bill is already a few digits long. It's super fun to sift through the bucket a few months later when you're trying to figure out if there's any real data in the bucket or just endless logs.