MongoDB to Kafka
real-time replication
TwinCommit replicates MongoDB to Apache Kafka in real time by reading the MongoDB transaction log and applying every committed change exactly once and in commit order. Use it to publish every committed MongoDB change as an event stream, with no triggers or capture tables on the source.
MongoDB
log reader
commit-ordered · exactly-once
Kafka
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 Kafka
Each source transaction is published with Kafka transactions, so consumers using read_committed never see a partial transaction. Messages are keyed by primary key in JSON, Avro or Protobuf.
Requirements
- ✓A topic naming template
- ✓Producer ACLs including transactional.id
- ✓Optional Schema Registry for Avro and Protobuf
Setup
Set up MongoDB → Kafka 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 Kafka
Add a target block for Kafka. 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: kafka
bootstrap_servers: broker-1:9092,broker-2:9092
topic: "{schema}.{table}"
format: avro
schema_registry: http://registry:8081
tables:
- source: sales.orders
- source: sales.customersMongoDB to Kafka replication FAQ
How does TwinCommit replicate MongoDB to Kafka?
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TwinCommit reads changes from the MongoDB transaction log, buffers them per transaction, and applies each committed transaction to Kafka in commit order. Each source transaction is published with Kafka transactions, so consumers using read_committed never see a partial transaction. Messages are keyed by primary key in JSON, Avro or Protobuf.
Does MongoDB to Kafka 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 Kafka replication exactly-once?
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Yes. TwinCommit commits its checkpoint in the same Kafka 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.
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