database-migrations

Zero downtime database migrations require separating schema changes (DDL) from data migrations (DML), applying expand-contract patterns, and testing against production-sized data to avoid locks during PostgreSQL deployments.

Handling data backfills during schema changes requires isolating data transformations from DDL, batching updates to minimize lock contention, and verifying row counts against production-sized datasets before completing the migration.

Prisma and Django can be used for safe schema migrations by following principles like deployed migration immutability, separating DDL and DML, and planning rollbacks to ensure changes can be safely reverted without downtime.

Planning rollbacks for database schema changes involves writing backward-compatible migrations, testing reversion steps against production-sized data, and maintaining immutability of previously deployed migration files to ensure safe reverts.

You need to separate DDL and DML during database migrations when executing zero-downtime deployments, because mixing schema changes with data transformations causes table locks and blocks seamless production updates.