Zero-Downtime Database Migrations: Blue-Green Schema Strategies with Flyway
How to perform backward-compatible database schema changes, column renames, and table partitions in PostgreSQL without locking tables or dropping transactions.
Learn the Expand-Contract pattern for safely modifying production relational databases without requiring scheduled downtime maintenance windows.
The Expand-Contract Migration Pattern
To avoid breaking active application servers running previous code versions during a deployment, never drop or rename a column in a single step. 1) **Expand**: Add the new column as nullable. 2) **Write Dual**: Update application code to write to both old and new columns. 3) **Backfill**: Migrate historical records asynchronously. 4) **Contract**: Deprecate and drop the old column in a subsequent release.
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