Cassandra to S3
real-time replication
TwinCommit replicates Apache Cassandra to Amazon S3 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 S3 as open Delta Lake or Iceberg tables, with no triggers or capture tables on the source.
Cassandra
log reader
commit-ordered · exactly-once
S3
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 S3
Changes land as Apache Iceberg, Delta Lake or Parquet tables, one atomic commit per micro-batch with the checkpoint in the snapshot metadata. Iceberg tables register in AWS Glue or Amazon S3 Tables automatically.
Requirements
- ✓IAM role with s3:GetObject, PutObject, DeleteObject and ListBucket on the prefix
- ✓Glue catalog permissions for table registration
- ✓Same-region placement recommended
Setup
Set up Cassandra → S3 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 S3
Add a target block for S3. 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: s3
bucket: acme-lake
path: replica/{schema}/{table}
format: iceberg
catalog: { type: glue, database: replica }
tables:
- source: sales.orders
- source: sales.customersCassandra to S3 replication FAQ
How does TwinCommit replicate Cassandra to S3?
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TwinCommit reads changes from the Cassandra transaction log, buffers them per transaction, and applies each committed transaction to S3 in commit order. Changes land as Apache Iceberg, Delta Lake or Parquet tables, one atomic commit per micro-batch with the checkpoint in the snapshot metadata. Iceberg tables register in AWS Glue or Amazon S3 Tables automatically.
Does Cassandra to S3 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 S3 replication exactly-once?
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Yes. TwinCommit commits its checkpoint in the same S3 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 S3 today.
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