Approach
Legacy migration approach
The same three ideas apply on every engagement, whatever system is in front of us. Together they keep each step small, checked and reversible.
Move one slice at a time
Switching everything to a new system at once means the whole business depends on that one switch going right. We move traffic to the new system gradually, one part at a time, so a problem stays contained to that part and can be fixed or rolled back on its own. This is often called the strangler-fig pattern. The plan can look longer on paper, but it avoids the long outages a big-bang switch risks when something unexpected turns up.
Run old and new side by side
Before the new system handles real traffic, it runs in parallel with the old one. Writes go to both, and we compare the results continuously until they match. This dual-write verification gives you ongoing evidence, under real production load, that the new system produces the same answers as the old one.
Keep a tested way back
Cutover day follows a written runbook, and the runbook always includes the way back. We rehearse the rollback before go-live, the same way we rehearse the cutover itself, so it can be relied on if it's ever needed. The aim is a cutover day where nothing surprising happens.
Tools, including AI
We use modern tooling, including AI, where it makes the work faster, safer and more reliable. Every change still goes through the same review, tests and verification, whoever or whatever wrote it, and you see the same evidence either way.