Cassandra to Synapse
real-time replication
TwinCommit replicates Apache Cassandra to Azure Synapse Analytics in real time by reading the Cassandra transaction log and applying every committed change exactly once and in commit order. Use it to feed Synapse with live Cassandra data for analytics, AI and reporting, with no triggers or capture tables on the source.
Cassandra
log reader
commit-ordered · exactly-once
Synapse
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 Synapse
Micro-batches are staged as Parquet in Azure Data Lake Storage, loaded with COPY INTO and applied with MERGE in one transaction together with the checkpoint. Tables are created hash-distributed on the primary key.
Requirements
- ✓An ADLS Gen2 staging container
- ✓A service principal or managed identity with db_ddladmin and db_datawriter
- ✓ADMINISTER DATABASE BULK OPERATIONS for COPY INTO
Setup
Set up Cassandra → Synapse 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 Synapse
Add a target block for Synapse. 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: synapse
server: acme-dw.sql.azuresynapse.net
database: replica_dw
auth: managed_identity
staging: abfss://staging@acmelake.dfs.core.windows.net/twincommit/
tables:
- source: sales.orders
- source: sales.customersCassandra to Synapse replication FAQ
How does TwinCommit replicate Cassandra to Synapse?
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TwinCommit reads changes from the Cassandra transaction log, buffers them per transaction, and applies each committed transaction to Synapse in commit order. Micro-batches are staged as Parquet in Azure Data Lake Storage, loaded with COPY INTO and applied with MERGE in one transaction together with the checkpoint. Tables are created hash-distributed on the primary key.
Does Cassandra to Synapse 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 Synapse replication exactly-once?
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Yes. TwinCommit commits its checkpoint in the same Synapse 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 Synapse today.
Download the free Developer edition, or have one of our replication engineers walk you through a migration plan.