MongoDB to PostgreSQL
real-time replication
TwinCommit replicates MongoDB to PostgreSQL in real time by reading the MongoDB transaction log and applying every committed change exactly once and in commit order. Use it to migrate or continuously mirror MongoDB into PostgreSQL with zero downtime, with no triggers or capture tables on the source.
MongoDB
log reader
commit-ordered · exactly-once
PostgreSQL
native writer
How capture works on MongoDB
TwinCommit opens change streams on replica sets and sharded clusters, persists resume tokens with the checkpoint, and keeps multi-document transactions intact.
Prerequisites
- ✓Replica set or sharded cluster (change streams need an oplog)
- ✓changeStream and find privileges on watched databases
- ✓Pre- and post-images enabled for full before/after values (optional)
How apply works on PostgreSQL
Binary COPY into staging plus INSERT … ON CONFLICT, with the checkpoint in the same transaction.
Requirements
- ✓wal_level = logical
- ✓REPLICATION privilege
- ✓Primary key or REPLICA IDENTITY FULL
Setup
Set up MongoDB → PostgreSQL in four steps
- 1
Prepare MongoDB
Run twincommit check. It verifies replica set or sharded cluster (change streams need an oplog) and the other prerequisites, and prints the exact fix for anything missing.
- 2
Point at PostgreSQL
Add a target block for PostgreSQL. TwinCommit can generate target DDL with twincommit ddl -apply.
- 3
Snapshot
twincommit snapshot copies each table under a brief share lock and records the exact log position.
- 4
Stream
twincommit run streams every committed change from that position, exactly once and in commit order.
source:
type: mongodb
uri: ${MONGODB_URI}
target:
type: postgres
dsn: ${PG_DSN}
tables:
- source: sales.orders
- source: sales.customersMongoDB to PostgreSQL replication FAQ
How does TwinCommit replicate MongoDB to PostgreSQL?
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TwinCommit reads changes from the MongoDB transaction log, buffers them per transaction, and applies each committed transaction to PostgreSQL in commit order. Binary COPY into staging plus INSERT … ON CONFLICT, with the checkpoint in the same transaction.
Does MongoDB to PostgreSQL replication need triggers or capture tables?
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No. TwinCommit reads the MongoDB log directly and creates no objects in the source database.
Is MongoDB to PostgreSQL replication exactly-once?
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Yes. TwinCommit commits its checkpoint in the same PostgreSQL transaction as the data, so a crash or restart never loses or duplicates a transaction.
What MongoDB versions are supported?
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MongoDB 5.0–8.x · MongoDB Atlas · replica sets and sharded clusters.
Stream MongoDB to PostgreSQL today.
Download the free Developer edition, or have one of our replication engineers walk you through a migration plan.