In my opinion the trick to large-scale software architecture is to build small software systems tied together by strictly defined interfaces. There are many way

In my opinion the trick to large-scale software architecture is to build small software systems tied together by strictly defined interfaces. There are many ways to ensure the strictness of the interface: having strict typing and a compilation step, unit tests, static code validation (compiling without compiling), and even hungarian notation and systematic code reviews. Those are not mutually exclusive tools; quality improves with each one added, but none are mandatory. My personal experience working on large systems without unit tests (among others a 200.000 line javascript codebase) is that as long as you adopt good coding practices around how you define clearly typed interfaces the lack of unit tests doesn't hurt you that badly and there is no wild-growth of bugs. Using the jetbrains IDE's also made a big difference for me due to the static code checking. I want to see the little code quality box at the top of the scrollbar turn green, and the process of doing that tends to weed out a lot of those bugs that a unit test or a strict type system would catch. I do think that if you're building large-scale or long-lived systems, it is not any faster to use a dynamically typed language. I've written lots of code in both strictly typed and loosely typed languages, and I find that while I enjoy a loosely typed language more, I am equally productive in the strictly typed environment because strict typing makes it easier to write reliable code from the outset.