What is Database Migration?
A database migration is a versioned, incremental change to your database schema — adding a column, creating a table, or modifying indexes. Migrations let your schema evolve alongside your code safely.
In plain English
Database migrations are like renovation permits for your building. Before knocking down a wall or adding a room, you file a permit (write a migration), get it approved (test it in staging), and have a plan to undo the work if something goes wrong (rollback migration). Ad-hoc renovations without permits lead to structural problems.
How it works
Migrations are SQL scripts or ORM-generated files stored in your codebase alongside your application code. A migration runner (like Flyway, Liquibase, or Prisma Migrate) tracks which migrations have been applied and runs pending ones in order. Rolling back reverts the most recently applied migration.
Why it matters for AI-built apps
AI-generated ORMs and schema changes often skip the migration layer, leading to manual database edits that aren't tracked anywhere. This makes it impossible to reproduce the schema in staging or recover after a botched change. Proper migrations make your schema as reproducible and auditable as your code.
Best practices
Never modify an already-applied migration — always create a new one. Write backward-compatible migrations when possible: add a column as nullable before making it required. Always test migrations on a staging database with production-like data volume before running them in production.
Frequently asked questions
Can I run migrations automatically on deploy?
Yes, and it's a best practice. Run migrations as a pre-deploy step in your CI/CD pipeline, but ensure they're backward compatible so the old code version keeps working during the transition.
What if a migration fails halfway through?
Run migrations inside transactions where possible so a failure rolls back automatically. For operations that can't be transactional (like adding indexes), monitor and have a rollback script ready.
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