A developer spent weeks rewriting a production service built on Cake PHP simply because the framework felt unfamiliar. He replaced each component with Laravel equivalents, merging the new code and launching the next project in Laravel. The rewrite offered no performance gain, no new feature, and no measurable business value—personal satisfaction.

The author argues most rewrites serve engineers’ curiosity or résumé goals, not the company’s bottom line. Production code accumulates “scar tissue” – hidden bug fixes, timeout tweaks, and conditional workarounds documented only in tickets or Slack threads. Discarding that history forces teams to rediscover the same issues, paying twice for problems already solved. Only when a runtime reaches end‑of‑life or a CVE appears does the balance tip toward replacement.

When a service must support a capability it was never designed for, the author now uses an AI coding agent to generate the replacement. While the model writes code fast, it cannot capture the undocumented fixes that kept the original stable, so the new version inherits the same hidden bugs. The decisive test for any rewrite remains a concrete cost metric, not aesthetic preference.