Cassandra to Redis
real-time replication
TwinCommit replicates Apache Cassandra to Redis in real time by reading the Cassandra transaction log and applying every committed change exactly once and in commit order. Use it to keep a Redis cache exactly in sync with Cassandra, with no triggers or capture tables on the source.
Cassandra
log reader
commit-ordered · exactly-once
Redis
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 Redis
Each row is written as a Redis hash (or JSON document) under a key template such as `orders:{ORDER_ID}`, with deletes removing the key. Optionally every change is also appended to a Redis Stream.
Requirements
- ✓A key template per table
- ✓ACL user with write access to the key prefix
- ✓TLS endpoint recommended
Setup
Set up Cassandra → Redis 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 Redis
Add a target block for Redis. 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: redis
url: rediss://cache.internal:6380
key_template: "{table}:{pk}"
format: hash
tables:
- source: sales.orders
- source: sales.customersCassandra to Redis replication FAQ
How does TwinCommit replicate Cassandra to Redis?
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TwinCommit reads changes from the Cassandra transaction log, buffers them per transaction, and applies each committed transaction to Redis in commit order. Each row is written as a Redis hash (or JSON document) under a key template such as orders:{ORDER_ID}, with deletes removing the key. Optionally every change is also appended to a Redis Stream.
Does Cassandra to Redis 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 Redis replication exactly-once?
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Yes. TwinCommit commits its checkpoint in the same Redis 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 Redis today.
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