Why Legacy Migration Fails
Most enterprise migration projects fail not because of technology, but because of scope. Teams try to replace everything at once, underestimate data complexity, and go dark on users for too long.
The result: delayed go-lives, cost overruns, and a new system that nobody trusts.
The Strangler Fig Pattern
The most reliable migration strategy is the Strangler Fig — you grow the new system around the old one, gradually routing traffic to the new system while the legacy continues running.
This means:
- Users see continuity, not big-bang cutover
- You can roll back individual features, not the entire migration
- The new system is tested with real production data before it's fully live
Data Migration Is the Hard Part
Code is easy to rewrite. Data is not. A 10-year-old system has a decade of schema drift, inconsistent records, and business logic baked into database stored procedures nobody documented.
Our process:
1. Audit the data — understand the actual shape of production data, not just the schema
2. Write idempotent migration scripts — scripts you can run multiple times without side effects
3. Run in parallel — write to both old and new systems during transition
4. Reconcile — automated diff reports to catch divergence before cutover
Handling the Human Side
Your team knows the old system. They have workarounds for its bugs. They'll resist the new system even if it's objectively better.
Invest in training, document the new system clearly, and involve power users early in UAT. The system is only as good as its adoption.
What a Realistic Timeline Looks Like
A mid-size enterprise system (200–500 users, 10+ modules) typically takes 12–18 months to migrate properly. Projects that claim 6 months either descend into chaos or deliver something that doesn't fully replace the old system.
Budget for a parallel-running period of 3–6 months where both systems are live.
We've guided several enterprises through this process. If you're planning a migration, [reach out](#contact) — the decisions made in the first 60 days determine whether you succeed.