Speed tuning explained simply

Writing this up while it is fresh, because I will forget the details otherwise. I do not want to sink more time or money into it before I understand what I am optimising for.

It behaves as expected on one account and not on another, same device. If someone has a link to a proper explanation, I will take it.

Not the answer you want, but this changed for me after the last patch, so older threads may steer you wrong.

Others may have a cleaner method.

In my testing, ignore the loudest advice; the boring answer is usually the correct one here.

In my testing, the averages hide the problem; look at the one percent lows instead.

Worth checking first: it is almost always a setting rather than hardware, so try the free fixes before spending anything.

For what it is worth, worth testing on a second account to rule out something profile-specific.

Worth a shot before anything drastic.

I went through this last month. do the cheap diagnostic first — it costs nothing and rules out half the causes.

Worth a shot before anything drastic.