Scaling & legacy
Three fracture planes for safer legacy migration
Legacy migration becomes safer when the organisation is clear about why it is changing, what behaviour must be understood, and how capability can move incrementally.
1. Measurable business motivation
Modernisation should begin with a business outcome, not a technology preference. Define the change in terms such as faster, fewer, more, or less, and attach a measurable value where possible.
2. Problem-space understanding
Before moving code, understand the capability, behaviour, rules, dependencies, coupling, and natural interception points. Domain-driven design, runtime evidence, lineage analysis, and behavioural characterisation help establish confidence in what the system really does.
3. Gradual and reversible movement
Move behaviour in small slices. Preserve options, create compensating actions where rollback is impossible, and use seams, APIs, or interception points to reduce the blast radius of each step.
Migration is a learning system
The plan should evolve as evidence improves. The goal is not perfect upfront knowledge, but enough confidence to make the next safe decision while continuously reducing uncertainty.