Big-bang rewrites fail quietly for years before they fail loudly in production. Institutions cannot afford either timeline. Modernization succeeds when each increment delivers operator-visible value.
Strangle with intent
The strangler fig pattern only works with explicit retirement criteria. We define what “done” means for each slice: traffic percentage, error budget, and data parity checks — not just “new service exists.”
- Start at integration seams with the highest change frequency.
- Dual-write with reconciliation jobs before cutover.
- Keep rollback switches until two release cycles pass clean.
Modernization is a delivery program, not a architecture poster. Treat it that way and stakeholders stay aligned when the work gets unglamorous.