Polled monitoring is where the application performing the monitoring task is querying the service at a set interval and evaluating the state of the service at that moment in time. Polled monitoring is relatively simple to implement and typically far less costly than real-time or stream monitoring in terms of both overhead and dollars. Though simpler and less costly than stream monitoring, polled monitoring has the following issues:

If we have a polled monitoring solution with an interval of five minutes (300 seconds), the worst case response time to an event is 300 seconds—the worst case response time is the polling interval. This is the response time to determine something has to be done and includes the time the system takes to actually respond to the event in addition to the up to 300 seconds it took to detect the event.