Cassandra to Kafka
real-time replication
TwinCommit replicates Apache Cassandra to Apache Kafka in real time by reading the Cassandra transaction log and applying every committed change exactly once and in commit order. Use it to publish every committed Cassandra change as an event stream, with no triggers or capture tables on the source.
Cassandra
log reader
commit-ordered · exactly-once
Kafka
native writer
How capture works on Cassandra
TwinCommit tails the CDC commit-log segments on every node, deduplicates replica writes, and orders mutations by write timestamp per partition.
Prerequisites
- ✓cdc_enabled: true in cassandra.yaml
- ✓WITH cdc = true on replicated tables
- ✓Agent sidecar or shared volume access to cdc_raw on each node
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 Cassandra → Kafka in four steps
- 1
Prepare Cassandra
Run twincommit check. It verifies cdc_enabled: true in cassandra.yaml 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: cassandra
contact_points: [cass-1, cass-2, cass-3]
cdc_dir: /var/lib/cassandra/cdc_raw
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.customersCassandra to Kafka replication FAQ
How does TwinCommit replicate Cassandra to Kafka?
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TwinCommit reads changes from the Cassandra 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 Cassandra to Kafka replication need triggers or capture tables?
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No. TwinCommit reads the Cassandra log directly and creates no objects in the source database.
Is Cassandra 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 Cassandra versions are supported?
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Apache Cassandra 4.0, 4.1, 5.0 · DataStax Enterprise 6.8+ · Astra DB (target) · ScyllaDB (target).
Stream Cassandra to Kafka today.
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