Speeding up your older iPhone is one of the most satisfying improvements when performance is starting to flag, which can happen when you're using iOS 9 on an older phone. It can really slow it down – but this simple trick may help speed it up.
Clearing the memory cache within Apple's App Store should give you a suitable speed boost on any iPhone or iPad.
When within the App Store, you need to press down on any of the five tab buttons along the bottom of the screen 10 times in a row to clear the cached memory.
If you hit the same button 10 times, the screen will go white for a moment, reboot onto the main app store page and then the memory will be cleared.
As well as giving a speed boost to your iPhone or iPad, it should also kick any stuck app updates back into downloading.