Legacy modernization
Read an undocumented system and change it in steps, without stopping it.
SYNOPSIS
legacy [--read] [--map] [--migrate] [--verify]DESCRIPTION
No big-bang rewrite. The running system stays as it is while parts move to the new implementation, and each move is compared against the old behavior.
It starts with reading the code. Without documentation, we recover intent from the code, the data, and the operating logs.
SCOPE
- Reading the code
- Module boundaries, call relationships, and hidden rules, turned into a dependency map.
- Migration design
- What moves first and what stays, ordered by risk.
- Incremental move
- Old and new run side by side while traffic and features move over in parts.
- Behavior comparison
- Same input, same output, with every difference recorded.
DELIVERABLES
- Dependency map
- Migration order and risk list
- Behavior comparison results
- Post-migration operating procedure
FIT
Good fit
- You inherited a system with no design docs and no one left who knows it
- It cannot be stopped, so it can only be changed in steps
Not a fit
- You want a new front end on top of unchanged functionality