How much additional time does it take a key remapping app to convert volume up to keystroke A?

[Android Central Question]

If I use a key remapping app like Key Remap to remap my volume up button to a keystroke I'm assuming the key remapping app takes a bit of time to intercept the native action and then convert it to the requested action, in this case a key stroke.
So my question is how much additional time does it take? It doesn't look like much but for my purpose fractions of a second will make a difference.