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.
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
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.
