Blog And News
Modernising Legacy Platforms
Big-bang rewrites fail so reliably they have their own folklore. The alternative — the strangler pattern — replaces a legacy system piece by piece while it keeps running and earning.
Start at the edges
Pick a bounded, low-risk capability first: notifications, reporting, a single admin screen. Route it to the new stack behind a feature flag. Each slice proves the approach and funds the next one with credibility.
Freeze the old, feed the new
New features go to the new system only. The legacy codebase enters maintenance mode — bug fixes, no enhancements. This single rule prevents the migration from chasing a moving target forever.
Keep the data honest
Migrations die in data mismatches. We run old and new paths in parallel with automated comparison until the numbers agree for weeks, not days. Only then do we cut over — with a rollback plan rehearsed, not just written.
Expect it to take longer than the demo
A strangler migration is a marathon of small wins. Budget for it honestly, celebrate each retired module, and resist the urge to "just rewrite the rest" at 80% — that's exactly where rewrites go to die.