This is AWS Lambda function which can start and stop AWS RDS instances.

You an configure Cloudwatch rule to emit event which stops multiple instaces by theirs ids. Example of start event:

{
  "instances": ["test-instance-id-1", "test-instance-id-2"],
  "action": "start"
}

Example of stop event:

{
  "instances": ["test-instance-id-1", "test-instance-id-2"],
  "action": "stop"
}

Stopping instance will create RDS snapshot with name in format: "{instanceId}-{day}-{month}-{year}-{ticks}".