13. A system comprising: at least one processor; and program code configured to be executed by the at least one processor to cause the at least one processor to: maintain a plurality of pre-computed priced travel recommendations, each pre-computed priced travel recommendation having been previously computed based on underlying data obtained from a primary data source at a time that the pre-computed priced travel recommendation was computed; associate each pre-computed priced travel recommendation with a corresponding confidence factor that indicates a probability that the associated pre-computed priced travel recommendation is still valid, the pre-computed priced travel recommendation being valid if the underlying data in the primary data source has not changed in a time period passed since the time that the pre-computed priced travel recommendation was computed and being invalid if the underlying data in the primary data source has changed in the time period; receive a travel query from a client indicating at least one travel search criterion; identify, from the plurality of pre-computed priced travel recommendations, a set of pre-computed priced travel recommendations that comply with the at least one travel search criterion; evaluate the confidence factors associated with the identified set of pre-computed priced travel recommendations; validate the pre-computed priced travel recommendations for which the confidence factor is greater than a given threshold by querying the primary data source for valid database query results; and return to the client the set of pre-computed priced travel recommendations and the validated priced travel recommendations associated with confidence factors greater than the given threshold in a response to the travel query, wherein the probability the underlying data used to compute a respective pre-computed priced travel recommendation has changed increases as a function of a duration of the time period, and the response to the travel query is returned by sending a first message conveying the set of pre-computed priced travel recommendations and a second message conveying the validated priced travel recommendations associated with confidence factors greater than the given threshold.
13. A system comprising: at least one processor; and program code configured to be executed by the at least one processor to cause the at least one processor to: maintain a plurality of pre-computed priced travel recommendations, each pre-computed priced travel recommendation having been previously computed based on underlying data obtained from a primary data source at a time that the pre-computed priced travel recommendation was computed; associate each pre-computed priced travel recommendation with a corresponding confidence factor that indicates a probability that the associated pre-computed priced travel recommendation is still valid, the pre-computed priced travel recommendation being valid if the underlying data in the primary data source has not changed in a time period passed since the time that the pre-computed priced travel recommendation was computed and being invalid if the underlying data in the primary data source has changed in the time period; receive a travel query from a client indicating at least one travel search criterion; identify, from the plurality of pre-computed priced travel recommendations, a set of pre-computed priced travel recommendations that comply with the at least one travel search criterion; evaluate the confidence factors associated with the identified set of pre-computed priced travel recommendations; validate the pre-computed priced travel recommendations for which the confidence factor is greater than a given threshold by querying the primary data source for valid database query results; and return to the client the set of pre-computed priced travel recommendations and the validated priced travel recommendations associated with confidence factors greater than the given threshold in a response to the travel query, wherein the probability the underlying data used to compute a respective pre-computed priced travel recommendation has changed increases as a function of a duration of the time period, and the response to the travel query is returned by sending a first message conveying the set of pre-computed priced travel recommendations and a second message conveying the validated priced travel recommendations associated with confidence factors greater than the given threshold. 19. The system of claim 13 wherein the probability of a pre-computed priced travel recommendation result i being valid at a time t after a previous collection of the pre-computed priced travel recommendation i is given by e −λt , wherein λ i denotes a decrease rate of the probability of the pre-computed priced travel recommendation i being valid and t i denotes a time of since a last re-collection of the pre-computed priced travel recommendation i.