CloudWatch Insight to decrease lambda cost

- push metrics https://medium.com/tensult/send-lambda-functions-usage-metrics-to-amazon-cloudwatch-for-tuning-4d5ed69341b0
- https://forums.aws.amazon.com/thread.jspa?threadID=226674
-  https://cloudforecast.io/blog/aws-cloudwatch-fine-tune-lambda-functions/