Filter on existing database table results list

I have an existing webpage done in asp.net mvc/c#/razor that shows a list of results from the database. In the UI (the webpage) the following is needed: Two dropdown boxes - the first contains a list of departureids/departurenames and the second a list of transportids/transportnames (both contains plain static data) when an item is clicked in the dropdownbox it calls the server using ajax to get the list updated. The "default" sql query is done using "GROUP BY" - and shows the totalHolidays for each row (total matches to this destination) so code is needed to filter on this data. I want to avoid having to call the db to do the filtering so this should be done using a "cached" version.