Apache Cassandra vs Azure Cosmos DB for NoSQL

Apache Cassandra is a free, open-source NoSQL distributed database for mission-critical data and large active datasets. Its masterless architecture gives each node the same functionality. The project says read and write throughput can grow linearly as machines are added, without downtime or application interruption. Cassandra can run on premises, with one cloud provider, across multiple providers, or in a combination of those environments. It supports replication across data centers and configurable consistency levels for queries, along with CQL, transactions, and horizontal scaling. The project lists audit logging for DML, DDL, and DCL activity, and fqltool for recording and replaying production workloads. Drivers are available for Java, Go, Python, and Node.js; downloads include tarballs and packages, and installation guidance covers Debian and RPM. The ecosystem includes tools and connectors for Apache Kafka, Apache Flink, Apache Spark, and Kubernetes. The project identifies version 5.0 as the latest GA release and says it is maintained until the 8.0 release. Cassandra is self-managed, and listed third-party ecosystem projects are not supported by its community.

Azure Cosmos DB for NoSQL is a fully managed cloud database built around schema-agnostic JSON documents and SQL-like querying. It supports global data distribution, multi-region writes, and automatic failover, with configurable consistency controls and transactions. Search includes vector and hybrid similarity capabilities for workloads such as retrieval-augmented generation and AI agents. Throughput can use standard provisioned, autoscale provisioned, or serverless models. The service lists SDKs for.NET, Java, JavaScript/Node.js, Python, Go, and Rust. Its change feed can support event-driven architectures and streaming pipelines using Azure Functions and Spark; no-ETL analytical workflows are available through Azure Synapse Link or Fabric mirroring. Microsoft states that NoSQL data has service-level agreements including less than 10 millisecond read and write latency and 99.999 percent availability. A free tier includes 1,000 RU/s and 25 GB of storage for one account per Azure subscription, and a 30-day trial is listed. The Azure Cosmos DB emulator provides a no-cost local development environment for Windows or Linux. The pricing page notes that the selected compute pricing model and API cannot be changed after selection.