When XP says "go for the simplest possible design", what does that mean?
1. Simplest possible design to IMPLEMENT?
1. Simplest possible design to UNDERSTAND LATER?

An thread discuss how far should we go. Seen most people agree what should be done is "Simplest possible design to TEST and IMPLEMENT"

http://groups.yahoo.com/group/extremeprogramming/message/90466

It apply on feature, not on quality - http://martinfowler.com/bliki/Yagni.html

Don’t write reusable code - https://medium.com/@scott.boring.sb/dont-write-reusable-code-a857e925b683