Migrating a 6-Year-Old ERP Without a Single Day of Downtime

The Constraint That Shaped Everything

A manufacturing client needed to move off a 6-year-old PHP monolith. The catch: their order pipeline runs 24/7, and a botched cutover would mean missed shipments — not an acceptable tradeoff for a "modernization" project.

The Approach: Strangle, Don't Rewrite

Instead of a big-bang rewrite, we ran the old and new systems side by side for eleven weeks, routing traffic module by module as each one passed parity testing against the legacy system's actual production data:

• Inventory sync moved first — lowest risk, easiest to verify against known totals
• Order intake moved second, with a rollback switch kept live for three weeks after cutover
• Reporting and analytics moved last, once we trusted the underlying data fully

AI handled the repetitive part of this: generating the data-mapping layer between the old and new schemas, and drafting comparison scripts that flagged any record where the two systems disagreed. Our engineers wrote the cutover logic itself and made every go/no-go call.

The Result

Zero missed shipments during the migration window, and a system the client's own developers can now extend without calling us first for every change.