A Legacy Modernization Playbook That Respects the Legacy

Every modernization project I’ve worked on started with someone wanting to rewrite the legacy system, and none of them ended with a rewrite. What they ended with (the ones that shipped, anyway) was a service layer in front of the legacy application that let new consumers integrate against a modern API while the legacy system kept doing what it had done for years underneath. The rewrite fantasy is seductive because the legacy code is usually genuinely bad.