Azure Cosmos DB vs Firebase Realtime Database: What are the differences?

Azure Cosmos DB and Firebase Realtime Database are both NoSQL databases that offer real-time data synchronization and global scalability. Let's explore the key differences between them.

1. Data model: Azure Cosmos DB supports multiple data models, including SQL, MongoDB, Cassandra, Gremlin, and Table, allowing developers to choose the model that best fits their needs. On the other hand, Firebase Realtime Database uses a JSON-like data model, making it easier to work with for developers familiar with JavaScript's object notation.

2. Scalability: Azure Cosmos DB can horizontally scale both reads and writes across multiple regions, offering high availability and low latency globally. It utilizes built-in partitioning and multi-master replication to achieve scale and fault tolerance. In contrast, Firebase Realtime Database scales vertically by increasing the machine size, but it doesn't support automatic partitioning or multi-region replication out of the box.

3. Query capabilities: Azure Cosmos DB provides rich query capabilities, including support for SQL-like queries, stored procedures, and user-defined functions, making it a more powerful choice for complex queries and analytics. Firebase Realtime Database, on the other hand, offers limited querying capabilities with basic filtering and ordering options.

4. Transactions and consistency: Azure Cosmos DB offers multi-document ACID transactions, providing strong consistency guarantees across multiple documents or collections. It also supports five levels of consistency, allowing developers to choose between strong, bounded staleness, session, consistent prefix, or eventual consistency. Firebase Realtime Database, in contrast, doesn't provide built-in support for ACID transactions or strong consistency guarantees.

5. Integration with other Azure services: Azure Cosmos DB seamlessly integrates with other Azure services, such as Azure Functions, Azure Logic Apps, and Azure Event Grid, allowing developers to build serverless applications and leverage the full capabilities of the Azure ecosystem. Firebase Realtime Database, while it offers integration with Firebase Authentication and other Firebase services, doesn't have the same level of integration with external services.

6. Pricing and cost: Azure Cosmos DB pricing is based on the consumed resources, such as storage, throughput, and data transfer, providing flexible options to optimize costs. Firebase Realtime Database has a simpler pricing model based on the number of concurrent connections, storage, and data transfer, making it easier to estimate costs for smaller applications.

In summary, Azure Cosmos DB offers a more flexible data model, superior scalability, advanced query capabilities, ACID transactions, and deeper integration with Azure services. Firebase Realtime Database, on the other hand, provides a simpler JSON-like data model, vertical scalability, basic querying options, and easier cost estimation.