Are you using quick filters? If so, what type? Multiple Value List, Single Value List, Compact List, Sliders and any other future Quick Filter options that need to gather or display the domain of all selection options, must query the underlying datasource to build that domain. This may noticeably slow down the view render depending on the size of the domain. Wildcard Match, Custom Value Lists, and other Quick Filter options that do not display domains do not need to run this query and therefore allow faster renders.
This online help article can provide some more information as well:
Hope this helps a bit!
That helps. Thanks!