Hey @xjindf, sorting isn’t necessarily expensive. You can quite comfortably sort 10,000 elements or so on the CPU should not take too long.
here’s an example of 1500 particles being sorted each frame:
http://server1.lazy-kitty.com/tests/particles_sorting_2019_08_22
(see Particle engine for more detail)
It’s not always affordable, but when you have a small enough number of things to sort - it can be surprisingly cheap.