Hi,
I believe there are two answers:
a. You either hide the initial list and wait to show the result until it is fully loaded
b. You tweak you database to be a oiled and super slick database machine, but even then: when different searches need to be done it isdone sequentially I believe.
About a.
Super powerhouse user @romanmg did a video on how you can make this option happen. I looked for it, but could not locate it at the moment ( that woman is way to productive with helpful videos). Here is her Youtube channel: https://www.youtube.com/channel/UCTL_mXO3qsgFc_3s2T5wlWg
I will check again as well.
About b.
There are about a Cazillion reasons why pages or databases are not performing the way you want them. Here is a link to a discussion we had on it ( with in that discussion a link to the super helpful thread done by founder Josh on how to optimize performance):
I hope I did not send you into a rabbits hole with this one 