This change series enables features to be implemented in the new and old system without additional cost. This additionally reduces the risk of replacement project never finishing.
Habit: Shell System
Organization ROI: Always remain shippable, reduce risk from partially-done work. Engineer ROI: Migrate each feature into a working system, so you are done-done with a feature when you finish.
Habit: Explicit Dependencies
Organization ROI: Allow migrating features in any order, regardless of how entwined the code is with other features. Engineer ROI: Dependencies in the old system become obvious so they can be handled differently in the new system.
Habit: Dual-Home Features
Organization ROI: Continue shipping new features without delaying the legacy rewrite. Engineer ROI: Write new features once, in ways that work in both old and new systems.
Habit: Cross-System Sharing
Organization ROI: Reuse the good parts of your existing system even while creating a new system to replace the bad parts. Engineer ROI: Re-use code between old and new systems.
