Azure Cosmos DB vs Cassandra: What are the differences?

Azure Cosmos DB and Apache Cassandra are both popular NoSQL databases that are widely used for building scalable and highly available applications. Let's explore the key differences between them.

1. Consistency models: Azure Cosmos DB provides five well-defined consistency models, including strong, bounded staleness, session, consistent prefix, and eventual consistency. In contrast, Cassandra offers tunable consistency, where users can customize the level of consistency for each read and write operation.

2. Data distribution: Azure Cosmos DB uses a partitioning scheme called "container" to distribute data across multiple physical partitions automatically. This enables automatic load balancing and horizontal scalability. On the other hand, Cassandra has a decentralized architecture where data is partitioned and distributed across multiple nodes using a consistent hashing algorithm.

3. Multi-model capabilities: Azure Cosmos DB is a multi-model database that supports document, key-value, graph, and columnar data models, allowing developers to choose the best model for their application needs. Cassandra, on the other hand, primarily supports the columnar model, although some support for other models can be achieved through customizations and extensions.

4. Scalability and performance: Azure Cosmos DB offers elastic scalability with automatic partitioning and load balancing, enabling applications to scale seamlessly as the workload grows. It is also designed to deliver low-latency performance even at global scale. Cassandra provides linear scalability by adding more nodes to the cluster. However, scaling Cassandra requires manual configuration and management.

5. Global distribution: Azure Cosmos DB provides built-in support for global distribution, allowing data to be stored and accessed from multiple regions around the world with low latency. Cassandra, on the other hand, requires manual configuration and replication to achieve global distribution, making it more complex and time-consuming.

6. Backup and recovery: Azure Cosmos DB offers built-in backup and restore capabilities, allowing users to easily recover their data in case of a disaster or accidental data loss. Cassandra requires users to set up their own backup and recovery mechanisms, which can be more complex and time-consuming.

In summary, Azure Cosmos DB, a fully managed cloud-native database service, provides global distribution, multi-model support, and comprehensive SLAs, making it suitable for building globally distributed applications with low-latency access. Cassandra, an open-source distributed database, offers high availability, fault tolerance, and tunable consistency levels, providing flexibility in deployment and customization options for large-scale distributed systems.