THE IMPORTANCE OF THE DRY PRINCIPLE (Don't Repeat Yourself) is that it codifies the idea that every piece of knowledge in a system should have a singular representation. In other words, knowledge should be contained in a single implementation. The antithesis of DRY is WET (Write Every Time). Our code is WET when knowledge is codified in several different implementations. The performance implications of DRY versus WET become very clear when you consider their numerous effects on a performance profile.
following DRY helped us to find and repair a performance bottleneck that would have been more difficult to find had the code been WET.