Abstract: Methods, systems, and computer program products for watching availability-based data maintained in an external cache. Events that change a parameter for a first plurality of travel segment-dates are compared with a standard establishing a parameter value threshold. The events are filtered to produce a filtered set of events meeting the standard. An index correlating a second plurality of travel segment-dates in a travel domain with a plurality of travel solutions in the availability-based data is referenced to determine one or more of the second plurality of travel segment-dates in the index to which the events in the filtered set are applicable. The index is referenced to determine each travel solution correlated with the one or more of the second plurality of travel segment-dates. A notification is sent to the external cache to refresh the availability-based data to reflect each travel solution correlated with the one or more of the second plurality of travel segment-dates.