Yagni

By building this, we didn't build some other feature.

We could have been generating revenue two months earlier.

This is cost of delay.

The code for the presumptive feature adds some complexity.

It's harder to modify and debug, increasing the cost of other features.

This compounds over every future feature.

Accumulated technical debt

Ongoing costs to maintain, fix, or work around

Avoid any abstraction that makes it harder to understand the code's current requirements.

Apply yagni to extensibility hooks.

A lot of small yagni decisions add up to significant reductions in complexity to a code base,

while speeding up delivery of features that are needed more urgently.

Yagni is only a viable strategy if the code is easy to change.

Refactoring isn't a violation of yagni because refactoring makes the code more malleable, scalable, flexible.

Yagni has the curious property that it is both enabled by and enables evolutionary design.