Migrating from migrate-mongo

Already using migrate-mongo? You can switch in under a minute. mmk adopts your existing changelog as-is — no re-running migrations, no data loss, no rewriting files.

The one-command switch

mmk import     # one-time: adopt your migrate-mongo changelog (it is never modified)
mmk up         # applies only what's new — past migrations are recognized as already applied

Your applied history is preserved and new migrations run normally. Your up/down/create/status mental model carries over 1:1.

What mmk import does

mmk import reads your existing migrate-mongo changelog collection and records that history in the mmk changelog, so mmk up runs only what is new. It is one-time and forward-only, and the source collection is never modified.

• --from <collection> — source collection (default: changelog).
• --to <collection> — target collection (default: your config's migrationsCollection).
• --dry-run — preview the mapping, write nothing.
• --trust-hash — reuse migrate-mongo's fileHash instead of recomputing the checksum from disk.
• --force — import into a non-empty mmk changelog (batches continue after the current max).
• --no-lock — skip the concurrency lock (dev only).

Each imported migration gets a unique, sequential batch number; files on disk that are not in the source changelog stay pending.

See the full mmk import command reference.

Forward-only safety

Imported records are tagged origin: 'migrate-mongo'. Because their files use migrate-mongo's positional up(db, client) signature — which mmk's single-context-argument runner cannot execute safely — mmk down and mmk redo refuse them up front (before running or writing anything) with a clear reason. This guarantees the collection is never left half-reverted.

Going forward

New migrations you author with mmk create use the modern single-context signature and are fully reversible. Only the imported legacy records are forward-only.

Capability comparison

Capability	migrate-mongo	mongo-migrate-kit
up / down / create / status	✅	✅
Dry-run preview	❌	✅
Run a single migration file	❌	✅
Roll back a specific batch (not just the last)	❌	✅
redo (down + up)	❌	✅
SHA-256 checksum / tamper detection	❌	✅
Lifecycle hooks	❌	✅
First-class TypeScript (built-in)	❌	✅
History preserved on rollback (never deleted)	❌	✅