Filtering a view


I have a filtered view showing a list of courses. The raw list is very large with very many courses, so for the specific use (iframed into another site) the view is filtered with:{"match":"and","rules":[{"field":"field_27","operator":"is","value":"Børnehaveklassen","field_name":"Kategorier"}]}&view_127_page=1&view_127_sort=field_133|asc

It works as for the presentation, but the problem is that the dataset behind the view is still loaded completely by XHR, resulting in a very slow load time like several seconds.

This is obviously not a good UX so is it somehow possible apply the filter to the underlying dataset instead of only to the rendered display?