With good code structure, I see large Java projects compile small changes in seconds, even though compiling Java used to be a hog. You don't often rebuild from scratch during development, do you?
I was fixing an issue in one common library; properly testing changes required rebuilding and restarting a number of containers. Unit tests only tell you so much; you need proper integration tests to see how certain things interact.
If I were used a statically typechecked language (e.g. TypeScript), I could have eliminated 50%, or maybe 75% of the testing, because the compiler would check things for me before runtime. It would be drastically faster to localize and fix the bug even if the compilation increased build times 10x.
But the point is having a different view of what compilation means in the developer's workflow as a language designer. Having the engineer have to think about how to organize the code for the compiler is bad design unless that organization is built into the compiler. The compiler should reject programs that are not organized for optimal compilation. And the organization required at least does not impede understanding of the code (best if it improves it). This is Go's design imprimatur and it's critically important to the success of Go.
FWIW, I see large Java projects compile small changes take minutes to compile, even using hot-reload tools.
Figwheel in Clojure is not like this, however: they're doing something right there.
Making your code low-coupling if equally beneficial for the compiler and for the human to reason about the code. Hence modularization, limiting the visibility of parts, etc.
OTOH there are situations when you have to have a common interface which is used across the board. Imagine Java's `List` or `CharSequence`. If you touch it, you have to recompile all the innumerable uses of it. So the more pervasive the dependency is, the smaller and simpler and more fine-grained it should be. Java's `List` does not do a hugely good job in the compactness department; it's pretty stable, though. You want the same trait from your most foundational interfaces.
