Can anyone explain how someone can make a build system and not make correctness and speed the top priorities from the start? Once you do that parallelism is third feature you implement, the first being running an action, and the second being a hash based dependency graph of those actions inputs & outputs. Once you have that dependency graph parallelism and caching just appear pretty much for free.

It looks like google uses bazel (a parallel dependency graph based build) internally and they have 1-2 second rebuild times on apps much larger then Slack [0].

0 - https://medium.com/@Jakeherringbone/what-angular-is-doing-wi...