`guix environment` incurs an overhead:

--8<---------------cut here---------------start------------->8---
time /gnu/store/a462kby1q51ndvxdv3b6p0rsixxrgx1h-hello-2.10/bin/hello
Hello, world!

real	0m0.002s
user	0m0.002s
sys	0m0.000s
--8<---------------cut here---------------end--------------->8---

--8<---------------cut here---------------start------------->8---
$ time guix environment --ad-hoc hello -- hello
Hello, world!

real	0m0.921s
user	0m1.003s
sys	0m0.091s
--8<---------------cut here---------------end--------------->8---

It's possible to bypass this overhead by using --root:

--8<---------------cut here---------------start------------->8---
$ guix environment --ad-hoc hello --root=foo
[env]$ exit

$ source foo/etc/profile && time hello
Hello, world!

real	0m0.003s
user	0m0.003s
sys	0m0.000s
--8<---------------cut here---------------end--------------->8---

The above `source' is of course not containerized.

So is it possible to use a similar trick to run something containerized
"instantly", i.e.  with less than, say, 100ms overhead?

-- 
Pierre Neidhardt
https://ambrevar.xyz/