Phase 0 — Baseline and boundaries
Inventory executables, scheduled jobs, and manual spreadsheets that touch the system. Mark legal retention periods and “never down” windows. Output: scope charter signed by business and IT.
The migration phases we plan together
Every roadmap we deliver follows this skeleton. Dates and module names change; the order of risk reduction does not.
Phase 1 — Read-only discovery
Static analysis, log tracing, and paired walks with operators. No production writes. Output: dependency graph and heat map of change frequency.
Phase 2 — First vertical slice
Pick a module with clear inputs, limited downstream fan-out, and a business owner who can validate behaviour. Build the new path behind a facade or strangler routing layer.
Phase 3 — Dual running
Run old and new paths in parallel for a defined period. Compare outputs daily; agree tolerance for rounding and timing differences before go-live decision.
Phase 4 — Cutover and rollback rehearsal
Execute switch during an agreed window with rehearsed rollback. Operations owns the runbook; we observe and annotate gaps for the next slice.
Phase 5 — Decommission planning
Document what remains on legacy, why, and the triggers to retire it. Prevents “ghost” modules that nobody dares remove.
Ready for a roadmap tailored to your system?
Start with a legacy application assessment or request a scoping call if you already have architecture diagrams and need sequence validation.