Cassandra to SQL Server
real-time replication
TwinCommit replicates Apache Cassandra to Microsoft SQL Server in real time by reading the Cassandra transaction log and applying every committed change exactly once and in commit order. Use it to migrate or continuously mirror Cassandra into SQL Server with zero downtime, with no triggers or capture tables on the source.
Cassandra
log reader
commit-ordered · exactly-once
SQL Server
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 SQL Server
Set-based MERGE into BIN2-collated tables with an in-transaction checkpoint.
Requirements
- ✓FULL recovery model
- ✓Primary key on each replicated table
- ✓VIEW SERVER STATE and db_owner on the source database
Setup
Set up Cassandra → SQL Server 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 SQL Server
Add a target block for SQL Server. 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: sqlserver
dsn: ${MSSQL_DSN}
tables:
- source: sales.orders
- source: sales.customersCassandra to SQL Server replication FAQ
How does TwinCommit replicate Cassandra to SQL Server?
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TwinCommit reads changes from the Cassandra transaction log, buffers them per transaction, and applies each committed transaction to SQL Server in commit order. Set-based MERGE into BIN2-collated tables with an in-transaction checkpoint.
Does Cassandra to SQL Server 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 SQL Server replication exactly-once?
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Yes. TwinCommit commits its checkpoint in the same SQL Server 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 SQL Server today.
Download the free Developer edition, or have one of our replication engineers walk you through a migration plan.