Cassandra to ADLS
real-time replication
TwinCommit replicates Apache Cassandra to Azure Data Lake Storage in real time by reading the Cassandra transaction log and applying every committed change exactly once and in commit order. Use it to land live Cassandra data in ADLS as open Delta Lake or Iceberg tables, with no triggers or capture tables on the source.
Cassandra
log reader
commit-ordered · exactly-once
ADLS
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 ADLS
Each micro-batch becomes one atomic Delta Lake or Apache Iceberg commit (or Parquet files) with the checkpoint stored in the commit itself. Use merge mode to mirror current state, or append mode for a full change history.
Requirements
- ✓Storage Blob Data Contributor on the container
- ✓Hierarchical namespace enabled
- ✓Optional Iceberg catalog (REST or Hive Metastore)
Setup
Set up Cassandra → ADLS 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 ADLS
Add a target block for ADLS. 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: adls
account: acmelake
container: lake
path: replica/{schema}/{table}
format: delta
mode: merge
tables:
- source: sales.orders
- source: sales.customersCassandra to ADLS replication FAQ
How does TwinCommit replicate Cassandra to ADLS?
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TwinCommit reads changes from the Cassandra transaction log, buffers them per transaction, and applies each committed transaction to ADLS in commit order. Each micro-batch becomes one atomic Delta Lake or Apache Iceberg commit (or Parquet files) with the checkpoint stored in the commit itself. Use merge mode to mirror current state, or append mode for a full change history.
Does Cassandra to ADLS 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 ADLS replication exactly-once?
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Yes. TwinCommit commits its checkpoint in the same ADLS 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 ADLS today.
Download the free Developer edition, or have one of our replication engineers walk you through a migration plan.