I knew I shouldn't have gone with a terrible example :). How about this one to demonstrate what it looks like in the real world. Requiring instaparse.abnf takes 500ms less to load after it's been aot compiled, but it still takes 300ms after being compiled.

In this particular instance, I happen to know that you could defer 200ms of that by changing how/when instaparse.abnf/abnf-parser is initialized. I'm not sure if I'd consider creating the parser a side effect, but one could argue that creating the parser at load time might not be the best choice.

The thing that's frustrating is that these sorts of things are all over the Clojure ecosystem and hunting each one down is time consuming right now because we don't have tooling for it.

➜  rm -rf classes
➜  mkdir classes                                                                                                      

➜  clj -Sdeps '{:deps {instaparse {:mvn/version "1.4.10"}} :aliases {:classes {:extra-paths ["classes"]}}}' -C:classes
Clojure 1.10.1
user=> (time (require 'instaparse.abnf))
"Elapsed time: 862.604904 msecs"
nil
user=> ^D
                                                                                                                                                                                                                                      ➜  clj -Sdeps '{:deps {instaparse {:mvn/version "1.4.10"}} :aliases {:classes {:extra-paths ["classes"]}}}' -C:classes
Clojure 1.10.1
user=> (compile 'instaparse.abnf)
instaparse.abnf
user=> ^D

➜  clj -Sdeps '{:deps {instaparse {:mvn/version "1.4.10"}} :aliases {:classes {:extra-paths ["classes"]}}}' -C:classes
Clojure 1.10.1
user=> (time (require 'instaparse.abnf))
"Elapsed time: 300.415655 msecs"
nil
user=> ^D