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Elassandra
What it is
Elassandra combines Apache Cassandra storage with OpenSearch search inside each node. OpenSearch indices correspond to Cassandra keyspaces, documents map to rows, and indexed fields map to columns or cells. Cassandra remains the durable layer, allowing a local search view to be rebuilt from Cassandra state after a restart. The maintained line targets Apache Cassandra 4.0.x, OpenSearch 1.3.x, and Java 11. Applications can search through the OpenSearch HTTP API or CQL, with HTTP responses using standard OpenSearch-style formats. Schema can be created from an OpenSearch index, or existing Cassandra schema can be discovered through OpenSearch mappings. Data placement follows Cassandra token ownership, while replicas follow keyspace replication settings. Listed integrations include OpenSearch plugins, OpenSearch Dashboards, and Spark. Deployment options include tarball, Debian package, RPM, Docker image, and Helm chart. Elassandra is free and open source, with a 30-day trial noted.
For and against
For
- Distributed storage and search in each node
- OpenSearch HTTP API and CQL support
- Multiple deployment package options
- Cassandra-backed restart recovery
- Horizontal scaling and multi-region support
Against
- Requires the Murmur3 partitioner
- Search indexing adds work to Cassandra writes
- Immediate visibility can increase write latency
- Advanced upstream features require validation
The verdict
Elassandra offers a combined Cassandra and OpenSearch architecture with familiar search interfaces and several deployment paths. Its consistency, refresh, and feature-scope considerations matter during operational planning.
Who it suits
It suits teams that want Cassandra-backed distributed storage and OpenSearch-compatible search in a self-hosted deployment. Operators must use the Murmur3 partitioner.
On the record
- APIs
- Elassandra exposes Cassandra-backed documents through OpenSearch-compatible HTTP APIs and also supports searching through CQL.elassandra.org · read 3 Oct 2026
- Consistency limit
- Document version fields such as _version, _seq_no, and _primary_term are not globally authoritative conflict controls.elassandra.org · read 3 Oct 2026
- Current stack
- The maintained line targets Apache Cassandra 4.0.x, OpenSearch 1.3.x, and Java 11.elassandra.org · read 3 Oct 2026
- Data durability
- Cassandra is the durable storage layer, and Elassandra rebuilds the local search view from Cassandra state when needed.elassandra.org · read 3 Oct 2026
- Data model
- Elassandra maps OpenSearch indices to Cassandra keyspaces, documents to rows, and indexed fields to columns or cells.elassandra.org · read 3 Oct 2026
- Deployment
- The documentation lists tarball, Debian package, RPM, Docker image, and Helm chart installation options.elassandra.org · read 3 Oct 2026
- Deployment options
- The documentation lists tarball, Debian package, RPM, Docker image, and Helm chart installation options.elassandra.org · read 3 Oct 2026
- Durability
- Cassandra is the durable storage layer, and restart recovery replays Cassandra state and can rebuild the local search view.elassandra.org · read 3 Oct 2026
- Feature scope
- The current line focuses on embedded OpenSearch, and the documentation advises validating advanced upstream features before relying on them in production.elassandra.org · read 3 Oct 2026
- Index deletion limit
- Deleting an index removes search metadata and files but does not delete its backing Cassandra keyspace or table by default.elassandra.org · read 3 Oct 2026
- Integrations
- The documentation lists integration with OpenSearch plugins, OpenSearch Dashboards, and Spark.elassandra.org · read 3 Oct 2026
- Local resource guidance
- The quick start says each node usually needs around 1.5 GB to 2 GB of RAM for local demos.elassandra.org · read 3 Oct 2026
- Maintained stack
- The documented maintained line targets Apache Cassandra 4.0.x, OpenSearch 1.3.x, and Java 11.elassandra.org · read 3 Oct 2026
- Operational limit
- Elassandra requires the Murmur3 partitioner, and search indexing adds work to Cassandra writes, especially for complex documents.elassandra.org · read 3 Oct 2026
- Operational requirement
- Elassandra requires the Murmur3 partitioner.elassandra.org · read 3 Oct 2026
- Purpose
- Elassandra embeds OpenSearch inside Apache Cassandra so each node provides distributed storage and distributed search.elassandra.org · read 3 Oct 2026
- Refresh trade-off
- Immediate search visibility after a write trades off against write latency, and synchronous refresh adds cost.elassandra.org · read 3 Oct 2026
- Scaling
- Data placement follows Cassandra token ownership, and replica behavior follows Cassandra keyspace replication.elassandra.org · read 3 Oct 2026
