The team spent months migrating to the newest framework.
The old system was discarded.
The senior developer asked, “What did the old framework teach you that the new one cannot?”
And, “When you migrate code, what else travels with it?”
The Teaching Unfolds
Every few years, the software industry experiences a collective migration. React replaces Angular, which replaced Backbone. Django gives way to FastAPI. The old framework becomes “legacy,” and teams invest enormous resources moving to whatever comes next. We treat these migrations as purely technical exercises, measuring success in lines of code converted and tests passing. But the senior developer’s question reveals a deeper dimension to this work.
The old framework taught your team something. Perhaps it showed you the limits of certain architectural patterns. Maybe it revealed how your users actually interact with the system, as opposed to how you designed it. The bugs you encountered, the performance bottlenecks you solved, the workarounds you invented – all of these represent hard-won knowledge. When we migrate, we often lose this context. The new codebase looks clean and modern, but it no longer carries the scars that taught us what not to do.
The second question is even more profound: what else travels with your code? Technical debt doesn’t stay behind just because you switched frameworks. If your old system had poorly defined boundaries between components, your new one probably will too. If your team struggled with over-engineering or premature optimization, those habits migrate with you. We like to believe that a new framework gives us a fresh start, but we bring ourselves to every codebase we touch.
This koan isn’t arguing against migrations. Sometimes they’re necessary and valuable. But it invites us to approach them more mindfully. Before discarding the old system, extract its lessons. Document not just what the code does, but why it does it that way. Understand which problems were framework limitations and which were fundamental to your domain. The framework you choose matters less than the wisdom you carry forward.
The real question isn’t whether to migrate. It’s whether you’re learning as you go.