heady-migration-engine

Zero-downtime Postgres migrations with safe rollbacks are coordinated by applying versioned schema changes using expand-contract patterns, topological ordering, and a reversible up/down API to ensure deployments do not interrupt database availability.

Topological sorting resolves migration dependencies to apply database changes in a deterministic order. This prevents dependency violations during deployment, ensuring every pending migration is applied sequentially without breaking schema coherence.

Yes, Neon branch testing validates schema migrations before deployment. The engine checks migrations against a Neon branch and uses checksum-based drift detection to ensure the test schema matches your production database state before applying changes.

Migration checksums generate Ed25519-signed signatures to detect drift, while advisory locks prevent concurrent migration runs. Together, they guarantee that only one deployment process modifies the schema and any unauthorized changes are immediately flagged.

The best way to rollback a failed Postgres schema migration is using the reversible up/down API, which executes guarded down migrations. The migration history provides audit-ready logs to track exactly which versioned changes are reversed.

Yes, the migration engine works standalone without external dependencies. It relies entirely on Postgres features like advisory locks and internal logic for topological sorting, requiring only a Postgres database to apply migrations safely.