Spotlight on iOS (iPhone and iPad) can be a handy feature for those who use it, but for the rest it may mean, lost computing power that will lead to poor battery life on your iPhone or iPad.
Spotlight is basically the search function that is built-in into your device and keeps tracks of witch files do you have on your device so you can quickly find them, but not all iPhone users even know about such a function to begin with, having it working all day long to keep track of each file on your device consumes a lot of battery, It will drain your battery if not properly configured.
Here is how to disable spotlight and save those computing power and get better battery life as well.
On your device, Go to Settings > General > Spotlight Search. My recommendation is to turn off everything on this screen, from top to bottom if you are not planning to use either Siri suggestions or the spotlight function itself. Turn off (Toggle the green switch) for each App or the ones you don’t want to keep track of, Once done, Reboot / Restart your device and hopefully you will get a snappier device + better battery life.