Modernizing legacy systems without betting the business

Big-bang legacy rewrites fail more often than they succeed. Here is the phased approach that reduces risk while still delivering meaningful modernization.

The instinct to rewrite a legacy system from scratch is understandable — and usually a mistake. Big-bang rewrites carry enormous risk and frequently fail to ship.

The strangler-fig pattern — incrementally routing functionality to new services while the legacy system remains the system of record — consistently delivers better outcomes.

This guide walks through how to sequence a strangler-fig modernization, including how to handle shared data and avoid the common trap of running two systems indefinitely.