Simple Lambda to stop and start EC2 instances with attached Auto Scaling Group, this lambda is trigger by Cloud Watch Event Bridge based on cron expression and execute a script to set MinSize and DesiredCapacity of ASG to 0. I create 2 tags Minimum and Desired to store values to start.
So the instances will terminate, and start based in Event Bridge Schedule Expression:
start: "cron(0 10 ? * MON-FRI *)"
stop: "cron(55 23 ? * MON-FRI *)"
i.e. start instances Monday to Friday during business hours
Another way to do that is creating an Scheduled Action attached to Auto Scaling Group https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/application-autoscaling.html#ApplicationAutoScaling.Client.put_scheduled_action
After optimize costs from EC2 and ASG, we will try to reduce costs from Lambda that we builded. https://aws.amazon.com/blogs/compute/operating-lambda-performance-optimization-part-1/
https://aws.plainenglish.io/aws-lambda-best-practices-7454da49314d https://docs.aws.amazon.com/lambda/latest/dg/best-practices.html https://medium.com/platform-engineer/aws-lambda-functions-best-practices-f40b60596a0c