Ajax response time higher than with CI3

@Yoko

What version of PHP are you running?  Are the queries exactly the same between CI3 & 4?

PHP 7.4.2. But i did test with PHP 8 too - same results.
On my web app - yes, they were exactly the same db queries. But, as i said earlier, i even did tests with almost empty controller returning just a simple json array with one variable inside and time responses were higher too.

test were done on local machine or live server ?

They were done on local machine (MBPr 13' late 2013)

// edit: Ah i forgot. Test were done on newest Safari 14.1.2 and newest Firefox 91.0