Software engineering · 18 June 2026
When to modernize, and when to leave it
A rewrite is a business case. A strangler slice is a plan. Most systems need the second, and a written reason for the parts you will not touch.
Teams say “rewrite” when the system is embarrassing. Embarrassment is not a sequence. The business is still closing orders on the embarrassing system.
A practical test: can you name one user journey that hurts, and can you put a new implementation in front of it while the old one still runs? If yes, that is the first slice. If you cannot name the journey, you are not ready to replace anything.
Some systems should be left. A stable back-office job that changes twice a year does not earn a two-year rewrite. Wrap it, give it a caretaker, and spend the team on the journey customers feel.
Cloud Shastra writes the “leave it” list in the same document as the roadmap. It is the part clients thank us for a year later.