In the current version of trimcloud, this is how we define an idle resource:
                            
                            
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Idle EC2 == under 5% CPU utilization for a continuous 24 hour period.
                                 
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Idle RDS == 0 database connections for a continuous 24 hour period.
                                 
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Idle Elastic IP == not associated to an EC2 instance or associated to an EC2 instance that is no longer running.
                                 
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Idle Lambda Function == 0 invocations for a continuous 1 week period.