If you find searching in Spotlight on your iPhone or iPad is a little slow, you may want to consider disabling Slack indexing. Nick Heer of PixelEnvy found that after he tried this, Spotlight seemed to speed up once again.
A couple of things to consider: the first is that some people are experiencing terrible Spotlight performance on their iOS devices. But even within TMO’s small data set of staff, we all have Slack on our iOS devices, but don’t all have this Spotlight slowdown. That means Slack indexing may or may not be the cause of the problem. If you do have the problem, disabling Slack indexing may or may not fix it.
If you are experiencing a Spotlight slowdown and have Slack, and want to disable indexing, here’s how to disable it.
Disable Slack Indexing
Open Settings and go to General > Spotlight Search. Scroll down until you see Slack, and turn the switch off.
There are some reports suggesting that this bug has been fixed in iOS 10.3.2. If you’re seeing issues with Spotlight, try this and see if it works. If you don’t have Slack installed, then update iOS (which you should always do, anyway).