Discover first
Map users, interfaces, data, batch jobs, operational workarounds, contracts, dependencies and failure modes before selecting a replacement.
Open reference architecture
Legacy-System Modernisation Architecture
A phased approach that treats replacement as one option, not the default, and reduces migration risk through discovery, seams and measurable exit criteria.
Stabilise
Address critical backup, access, observability and recoverability gaps before introducing migration risk where practical.
Create seams
Use APIs, adapters, events or controlled data interfaces to isolate legacy behaviour and enable incremental replacement.
Strangle incrementally
Move bounded capabilities in measurable slices rather than attempting a single opaque big-bang rewrite.
Data migration
Profile source data, define canonical mappings, reconcile counts/values, retain lineage and rehearse rollback.
Parallel evidence
For critical functions, compare old/new outputs and operational performance until exit criteria are evidenced.
Decommission safely
Remove integrations, credentials, infrastructure and licences only after dependencies and retention obligations are resolved.
Measure outcomes
Track reliability, operating cost, cycle time, security exposure, user effort and change lead time against the original baseline.