On the table opposite me, a chap got my attention. He and his partner were curious about the power bank I was using to charge my iPhone and my laptop, and we got into a socially-distanced chat about tech.
Power banks. Drones. Phones.
It was at this point his partner got interested.
“My iPhone feels so slow lately.”
It was an iPhone 6s Plus. Pretty old as iPhones go, but will be supported by iOS 15 for another year, so it still had some life in it.
Also: Will your iPhone or iPad run iOS 15 or iPadOS 15?  Since it was still raining, and I was settling in with my third coffee – this one a decaf (shame on me) – I offered to help. Help was accepted.
In this situation, there are three tweaks that I suggest. These are the ones I turn to because they are the least noticeable for the user. I could suggest more drastic things. – like turning off background app refresh – but those can have a detrimental effect on usability. Before we tweaked anything, I suggested checking the battery (Settings > Battery > Battery Health) to make sure that iOS wasn’t throttling performance because of a worn battery.
It wasn’t, but better to check than to realize this after making a bunch of changes.
Now onto the tweaks.
These three tweaks won’t give you the performance of a new iPhone, but it might put off having to upgrade for another year or so.

1: Reduce transparency

This doesn’t do much to speed up a newer handset, but for an older iPhone that’s struggling, it can make the interface feel smoother and more responsive.
Settings > Accessibility > Display & Text Size and toggle Reduce Transparency to on.

2: Reduce motion

Another one of those tweaks that can really help out an older iPhone without compromising the experience much.
Settings > Accessibility > Motion and toggle Reduce Motion to on.

3: Free up space

This iPhone had 16GB of storage, which doesn’t allow much in the way of breathing room. And it was pretty jam-packed with apps and photos.
Fortunately, this iPhone’s owner was, like myself, quite an audiobook fan, and had gigabytes of books stored taking up space. Once I pointed out that these could be redownloaded at any time, a pile of already listened to audiobooks were deleted, freeing up tons of space.
Must read: I just found my lost AirTag… you’ll never guess where it went To see an overview of what’s using up space, go to Settings > General > iPhone Storage.
It’s worth bearing in mind that Apple considers anything under 1GB of free space to be low storage.

Wrapping up

After these three tweaks were done, I asked the owner to reboot the iPhone and see what they thought.
“It’s so much better,” was the response, which I think says it all.
This iPhone was behind on updates by a few months so, and there was a huge backlog of app updates, so I suggested that doing those wouldn’t be a bad idea either.
But since the rain was clearing, and I didn’t have the room for any more coffee, it was time for me to be off.