Data Migration Strategies
Learn how to move data safely when modernizing legacy systems using dual writes, backfills, validation, and zero-downtime cutover techniques.
Why Data Migration Is Hard
Modernizing a legacy system often means moving data to a new schema or database. Unlike code, data is stateful and irreplaceable — a botched migration can corrupt or lose customer data permanently.
This lesson covers strategies to migrate safely with minimal downtime.
Big Bang vs Incremental
Two broad approaches:
- Big bang — stop the system, migrate everything, switch over (risky, requires downtime)
- Incremental — migrate gradually while both systems run
For SaaS, incremental zero-downtime migration is almost always preferred.
All lessons in this course
- Strangler Fig Pattern
- Replatforming vs. Refactoring
- Gradual Rollouts & Testing
- Data Migration Strategies