You're going to lose that gained time as soon as your "build" includes running tests. And you'll need more tests because in dynamic langueses generally nothing

You're going to lose that gained time as soon as your "build" includes running tests. And you'll need more tests because in dynamic langueses generally nothing works until you check it with a test. Mixing lanuages is a waste. It makes everything harder operationally, technically and business wise. The solution to long builds is projects structure that supports caching and parallelism. No one ever changes more than couple thousands lines even in a multi million line project, so why would everything had to get rebuilt? I've seen ci pipelines building millions of lines in under a minute, no sweat.