Any rule can be set up as a change-triggered rule or as a periodic rule. A change-triggered rule is applied when AWS Config records a configuration change for any of the resources specified. Additionally, one of the following must be specified:
Tag Key:(optional Value): A tag key:value implies any configuration changes recorded for resources with the specified tag key:value will initiate an evaluation of the rule.
Resource type(s): Any configuration changes recorded for any resource within the specified resource type(s) will initiate an evaluation of the rule.
Resource ID: Any changes recorded to the resource specified by the resource type and resource ID will initiate an evaluation of the rule.
A periodic rule is initiated at a specified frequency. Available frequencies are 1 hr, 3 hr, 6 hr, 12 hr, or 24 hrs. A periodic rule has a full snapshot of current Configuration Items (CIs) for all resources available to the rule.