Azure Cosmos DB vs Azure Storage: What are the differences?

Azure Cosmos DB and Azure Storage are cloud-based storage services. They differ in terms of their data models, scalability, querying capabilities, and storage options. Here are the key differences between them:

1. Data Model: Azure Cosmos DB is a globally distributed, multi-model database service that supports various data models, including key-value, document, columnar, and graph. Azure Storage, on the other hand, primarily offers a simple object storage service with a key-value data model. It is designed for storing unstructured data such as blobs, files, queues, and tables.

2. Scalability: Azure Cosmos DB is built for global scalability and can automatically scale throughput and storage across multiple regions. It offers elastic scalability with fine-grained control over performance and cost. Azure Storage also provides scalability, but it requires manual configuration and management of storage accounts and blob containers to handle increased load. Scaling Azure Storage may involve sharding data across multiple storage accounts.

3. Querying Capabilities: Azure Cosmos DB supports rich query capabilities across various data models. It provides a SQL-like query language called SQL API for querying JSON documents. It also supports other APIs like Gremlin for graph data and MongoDB API for document-oriented querying. Azure Storage, on the other hand, does not offer built-in query capabilities. Retrieving data from Azure Storage typically involves directly accessing the stored objects using their unique keys.

4. Storage Options: Azure Cosmos DB provides storage for application data, along with built-in features like automatic indexing, data partitioning, and replication. It is a fully managed service that abstracts away the underlying storage implementation. Azure Storage, on the other hand, offers different types of storage options, including Blob storage for large object data, Queue storage for messaging, Table storage for structured NoSQL data, and File storage for file shares.

5. Consistency Models: Azure Cosmos DB offers multiple consistency models, allowing developers to choose the desired level of data consistency based on their application requirements. It provides options like strong consistency, bounded staleness, session consistency, and eventual consistency. Azure Storage, on the other hand, primarily provides eventual consistency for read operations. It may take some time for changes made to Azure Storage to propagate across different regions.

In summary, Azure Cosmos DB is a globally distributed database service with support for multiple data models, automatic scalability, rich querying capabilities, and various consistency models. It is suitable for applications requiring high performance, global reach, and flexible data models. Azure Storage, on the other hand, is a scalable object storage service focused on unstructured data storage. It provides storage options like blobs, queues, tables, and files, but lacks the querying capabilities and flexibility of Azure Cosmos DB.