The strangler fig pattern, in practice
Incremental migration sounds obvious until you have to route live traffic. Here is what it actually takes.
Every legacy replacement starts with the same promise: we will do it incrementally. Most end up as a big-bang rewrite anyway, because incremental migration demands infrastructure nobody budgeted for.
What incremental actually requires
You need a routing layer that can send a request to either system, a reconciliation process that compares outputs, and a rollback that takes seconds rather than a change-advisory board.
Parallel running is not optional
Run both systems against real traffic and compare results before you move anyone. The bugs you find in that period are the ones that would have been production incidents.
A. Siddiqui
Chief Technology Officer
Writes about platform architecture and delivery practice.
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