What's the largest factors in latency?

A) For startup of Julia itself
B) For running scripts

I know some workaround for B) such as -O0 or --compile=min which often goes too far (I’m looking for a middle-ground with as fast startup as Python), is there any reason that scripts can’t be precompiled, without going the extra step of making a package (and registering). I guess compiling, i.e. storing on disk, shouldn’t be the default (I believe it isn’t in Python either, for main script), but too me it seems it could be an option.

I know of DaemonMode.jl.

Most who compile their own sysimage to it to add stuff to it, so it pays off later, but might there be a lot of stuff not needed for your program, which slows stuff down? How long does it take to load all of the sysimage (presumably all of it needs to be read an processed)? Can it be cut down a lot, and does anyone have such a sysimage lying around?