Every legacy system was once a shiny new project. It solved real problems, made money, and became critical to the business. Now it's a decade old, running on unsupported frameworks, and nobody wants to touch it. Sound familiar?
The "big bang" fallacy
The temptation is to rewrite everything from scratch. Build a new system in parallel, then switch over. In theory, it's clean. In practice, it's a recipe for disaster. Rewrites take longer than expected, the old system keeps evolving, and by the time you're ready to switch, the new system is already outdated.
The strangler fig pattern
Instead of replacing the old system, you gradually grow a new one around it. Each new feature or module is built with modern technology. Over time, more and more functionality moves to the new system. The old system slowly shrinks until it can be retired.
A practical modernization roadmap
.NET-specific considerations
The good news: Microsoft has invested heavily in making migration paths smoother. From .NET Framework to .NET Core to .NET 8, there are tools and patterns to help. The .NET Upgrade Assistant can automate much of the mechanical work. But the real challenge is usually the business logic and data access patterns that have evolved over years.
Conclusion
Modernizing a legacy system is a marathon, not a sprint. The key is to keep delivering value while improving the foundation. Small, incremental steps add up to transformative change over time.