[angarg12]

Hard disagree. The system I'm talking about is the largest scale system I've worked with (millions of QPS, thousands of servers). We built it in such a way that we were able to rewrite entire parts of our stack easily and relatively safely. The techniques and tools to do it are widely available today.

[auggierose]

Good for you. Modular programming goes a long way, of course, but I'd say that your changes were then those that could be foreseen, for example by drawing the right modular boundaries from the start.