Backends

A backend is the optional place NSchema persists a snapshot of the last applied schema. It’s declared in a BACKEND config block, and it’s what enables:

• Offline planning. Run plan against the recorded snapshot, with out a database connection;
• Drift detection. Detect out-of-band changes in your deployed database schema;
• The state show command To inspect the recorded schema.

A backend is optional: with no BACKEND block, NSchema plans against the live provider every time. See Offline planning & state for when you want one.

Available backends

Backend	Page
Local file	Local file
Amazon S3	Amazon S3

Locking

NSchema locks the backend during write operations (apply, destroy, refresh) so concurrent runs can’t corrupt the recorded state. If a run is interrupted and leaves a stale lock behind, clear it with lock release once you’re sure no operation is still running.

This applies to every backend; the lock lives alongside the state it protects.