Modernizing a product without pausing growth

Rebuilt critical paths of a legacy application while keeping the product live and the team shipping.

Problem

Core features had become expensive to change. Velocity slowed. Customers still needed continuous improvement.

Strangler-fig modernization: isolate high-churn modules, introduce typed boundaries, migrate with dual-write where needed, measure before and after.

Deploy frequency improved. Lead time for critical features dropped. No multi-month freeze, no big-bang rewrite.

Modernization is a product risk problem, not only a tech debt one. Sequence work by business value, not by how ugly the code feels.