Apache Cassandra
activeby Apache Software Foundation · since 2008 · also known as Cassandra, C*
Masterless wide-column database built for always-on writes across data centers.
Overview
Cassandra is the Dynamo-meets-Bigtable database: a ring of equal nodes, tunable consistency per query, and an LSM storage engine that soaks up enormous write volumes without a single point of failure. It is the default open-source choice when you need multi-datacenter replication and linear write scaling, and it powers some of the largest deployments on the planet. Version 5.0 added Storage-Attached Indexes, vector search and the Unified Compaction Strategy; the 6.0 line (in alpha) brings Accord general-purpose ACID transactions. Expect to model tables per query and to invest in operations (repair, compaction, JVM tuning).
Strengths & trade-offs
Strengths
- +No single point of failure: every node accepts reads and writes
- +Multi-datacenter replication with per-query consistency levels (LOCAL_QUORUM, EACH_QUORUM)
- +LSM write path absorbs very high sustained write throughput
- +Storage-Attached Indexes and native vector search since 5.0
- +Vendor-neutral Apache project with a large managed-service ecosystem
Trade-offs
- −Query-first data modelling; no joins and limited ad-hoc filtering
- −Lightweight transactions (Paxos) are slow; full ACID transactions are still in the 6.0 alpha
- −Operational load: repairs, compaction tuning, tombstones and JVM GC
- −Read latency tails can suffer under heavy compaction or wide partitions
Great for
- +Write-heavy event and telemetry ingestion
- +Messaging and activity feeds
- +Multi-region user and device data
- +Time-series with TTL-based expiry
- +Fraud and personalisation features served at scale
Think twice for
- −Relational workloads needing joins or multi-row ACID
- −Small datasets that fit one Postgres node
- −Ad-hoc analytics
- −Teams without operational capacity for repairs and tuning
Capabilities
Native or official first-party support · 11 of 25 tracked
Scale & consistency
- Comfortable data size
- Massive · Multi-PB
- Horizontal scaling
- Native
- Multi-region
- Active active
- Transactions
- Limited ACID
- Consistency
- Tunable, Eventual
- Schema
- Strict
- Architecture
- Distributed, Multi primary, Client server
- Query languages
- CQL
Consistent hashing with vnodes; clusters of hundreds to thousands of nodes and multi-PB datasets are documented (Apple, Netflix).
Deployment
available on · AWS · Google Cloud · Azure · IBM Cloud
Ecosystem
Alternatives to Apache Cassandra
C++ rewrite of Cassandra with shard-per-core design; also speaks the DynamoDB API.
apache-cassandra vs scylladb →AWS's serverless key-value and document store with single-digit-millisecond reads at any scale.
apache-cassandra vs amazon-dynamodb →Serverless, CQL-compatible Cassandra service on AWS with no clusters to manage.
apache-cassandra vs amazon-keyspaces →Serverless Cassandra-as-a-service with vector search and a JSON Data API, now owned by IBM.
apache-cassandra vs datastax-astra-db →Google's managed wide-column store, the original Bigtable, with HBase API and SQL access.
apache-cassandra vs google-cloud-bigtable →Hadoop's Bigtable clone: strongly consistent wide-column tables on top of HDFS.
apache-cassandra vs apache-hbase →Apache Cassandra FAQ
What is Apache Cassandra?
Apache Cassandra is a wide-column database by Apache Software Foundation, first released in 2008. Cassandra is the Dynamo-meets-Bigtable database: a ring of equal nodes, tunable consistency per query, and an LSM storage engine that soaks up enormous write volumes without a single point of failure. It is the default open-source choice when you need multi-datacenter replication and linear write scaling, and it powers some of the largest deployments on the planet. Version 5.0 added Storage-Attached Indexes, vector search and the Unified Compaction Strategy; the 6.0 line (in alpha) brings Accord general-purpose ACID transactions. Expect to model tables per query and to invest in operations (repair, compaction, JVM tuning).
Is Apache Cassandra open source?
Yes. Apache Cassandra is open source. License: Apache License 2.0.
Does Apache Cassandra support ACID transactions?
Partly. Apache Cassandra offers limited ACID guarantees (for example, single-record or single-partition transactions), with tunable, eventual consistency.
Does Apache Cassandra scale horizontally?
Apache Cassandra scales horizontally out of the box, with built-in sharding or partitioning. It is comfortable at massive scale (Multi-PB). It supports active-active multi-region writes.
How can I run Apache Cassandra?
You can self-host it. Managed offerings include Astra DB, Amazon Keyspaces, Azure Managed Instance for Apache Cassandra and Instaclustr for Apache Cassandra. It is available on AWS, Google Cloud, Azure and IBM Cloud.
What is Apache Cassandra best for?
Apache Cassandra is a strong fit for write-heavy event and telemetry ingestion; messaging and activity feeds; and multi-region user and device data. Think twice for relational workloads needing joins or multi-row ACID.
What are the best alternatives to Apache Cassandra?
Common alternatives to Apache Cassandra include ScyllaDB, Amazon DynamoDB, Amazon Keyspaces, DataStax Astra DB and Google Cloud Bigtable. The right choice depends on your workload, scale and hosting; WhichDB's smart match ranks them against your requirements.
How popular is Apache Cassandra?
Apache Cassandra ranks #20 of 844 databases on the WhichDB Score (55.9/100), and #1 among wide-column databases. The score combines public adoption signals such as package downloads, GitHub activity, job posts and developer discussion.