PostgreSQL to MongoDB
real-time replication
TwinCommit replicates PostgreSQL to MongoDB in real time by reading the PostgreSQL transaction log and applying every committed change exactly once and in commit order. Use it to serve PostgreSQL data from MongoDB at scale without dual writes, with no triggers or capture tables on the source.
PostgreSQL
log reader
commit-ordered · exactly-once
MongoDB
native writer
How capture works on PostgreSQL
TwinCommit uses a logical replication slot with the built-in pgoutput plugin, so there is nothing to install on the server.
Prerequisites
- ✓wal_level = logical
- ✓REPLICATION privilege
- ✓Primary key or REPLICA IDENTITY FULL
How apply works on MongoDB
Relational rows become documents keyed by primary key and are written with bulkWrite upserts inside MongoDB transactions, together with the checkpoint.
Requirements
- ✓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)
Setup
Set up PostgreSQL → MongoDB in four steps
- 1
Prepare PostgreSQL
Run twincommit check. It verifies wal_level = logical and the other prerequisites, and prints the exact fix for anything missing.
- 2
Point at MongoDB
Add a target block for MongoDB. 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: postgres
dsn: ${SOURCE_DSN}
slot: twincommit
target:
type: mongodb
uri: ${MONGODB_URI}
database: replica
document_id: primary_key
tables:
- source: SALES.ORDERS
- source: SALES.ORDER_LINES
exclude_columns: [INTERNAL_NOTES]PostgreSQL to MongoDB replication FAQ
How does TwinCommit replicate PostgreSQL to MongoDB?
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TwinCommit reads changes from the PostgreSQL transaction log, buffers them per transaction, and applies each committed transaction to MongoDB in commit order. Relational rows become documents keyed by primary key and are written with bulkWrite upserts inside MongoDB transactions, together with the checkpoint.
Does PostgreSQL to MongoDB replication need triggers or capture tables?
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No. TwinCommit reads the PostgreSQL log directly and creates no objects in the source database.
Is PostgreSQL to MongoDB replication exactly-once?
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Yes. TwinCommit commits its checkpoint in the same MongoDB transaction as the data, so a crash or restart never loses or duplicates a transaction.
What PostgreSQL versions are supported?
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PostgreSQL 13–18 · Amazon RDS and Aurora · Azure Flexible Server · Cloud SQL · AlloyDB.
Stream PostgreSQL to MongoDB today.
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