Comparing Microsoft Azure DocumentDB, Cosmos DB, And MongoDB

Table of contents

Comparing Microsoft Cosmos DB With MongoDB
Global Clusters
Monitoring and Disaster Recovery
Security Controls
Support and Services

Cosmos DB is a fully managed NoSQL database offered on Microsoft Azure. It offers multiple front-end APIs, including one compatible with the MongoDB wire protocol. It is important to note that this API does not run any MongoDB code.

This is a high-level comparison of MongoDB Atlas and the Cosmos DB API for MongoDB. We strongly encourage readers to conduct their own research on how each system can serve their specific use case.

Azure Cosmos DB’s “API for MongoDB” supports two deployment options: Resource Unit (RU)- based Cosmos DB and dedicated instance-based Azure DocumentDB). Each is aimed at different use cases and differs in features and capabilities. In this comparison, we will also explore the main differences between RU and Azure DocumentDB deployments.

The table below shows how the different options stack up.

	MongoDB Atlas	Microsoft Cosmos DB Imitation API for MongoDB
Choice of cloud providers	Yes. AWS, Azure, and Google Cloud	No
Integrated text search, geospatial processing	Yes	Yes, in Azure DocumentDB. Not available in RU deployments.
Supports all MongoDB features with full application compatibility	Yes. Runs native MongoDB	No. Does not run MongoDB server-side code
Access to the latest MongoDB version	Yes. Runs the latest release of MongoDB or any supported previous versions	No. The Cosmos DB MongoDB API does not offer full support for the latest MongoDB version
Free tier	Yes. 512 MB of memory and 5 GB of storage	Yes. For the Azure DocumentDB free cluster tier, high availability is not available, along with other limitations.
JSON data type support	BSON (Binary JSON). Optimized JSON format with native long, double, float, decimal, date, and time data types	BSON. Some data types have restrictions, including the inability to modify them once set in the RU provisioning model
Maximum document size	16 MB	16 MB
JSON schema for data governance controls	Yes	No. All schema controls must be written in the app tier
Blend data with joins and unions for analytics queries in the native query language	Yes	No
Replica set configuration	Up to 50 replicas by default; expandable upon request. All replicas are configured as data-bearing nodes	Azure DocumentDB deployments offer 2 replicas per replica set in High Availability mode
Automatic sharding support	Yes. Scales writes horizontally across multiple nodes. Able to store multiple TB of data on every shard. Enables users to refine the shard key as application requirements evolve.	Yes, in RU deployments. Sharding in Azure DocumentDB deployments supports fewer shards per cluster compared to MongoDB Atlas.
Pause and resume clusters	Yes	No
Database supported in on-premises and hybrid deployments	Yes. MongoDB Enterprise Advanced	No

Global Clusters

	MongoDB Atlas	Microsoft Cosmos DB imitation API for MongoDB
Multi-cloud deployment	Yes. Deploy across 125+ AWS, Azure, and Google Cloud regions	No. Cosmos DB users are limited to Azure only
Active-active clusters supporting global writes (Low-latency writes from anywhere in the world)	Yes	Yes
Cross-region replication; distribute data around the world for multi-region fault tolerance and local reads	Yes	Yes

Monitoring and Disaster Recovery

	MongoDB Atlas	Microsoft Cosmos DB Imitation API for MongoDB
Automatic scaling of compute and storage for all configurations	Yes	Yes, RU autoscaled (50% upcharge), Storage scaling in Azure DocumentDB is manual. Compute scaling is manual for all tiers except M200, which can scale from M80 to M200.
Monitoring of database health with automated alerting	Yes	Partial
Backup snapshots with on-demand Point in Time restore	Yes	Yes

Security Controls

	MongoDB Atlas	Microsoft Cosmos DB imitation API for MongoDB
Granular role-based access control	Yes	Yes
Encryption of data in-flight	Yes. TLS/SSL as standard	Yes
Encryption of data at-rest	Yes	Yes
Client-side field level encryption. Encryption of data in-use. Data not readable by service provider	Yes. Fully supported through automatic encryption	Yes. Separate implementation with limitations
Queryable Encryption; data encrypted on the client side can be queried without decryption	Yes	No
LDAP Integration	Yes	Yes
Database-level auditing; track DDL, DML, DCL operations	Yes	Yes
Bring your own KMS	Yes	No. Azure key vault only

Support and Services

	MongoDB Atlas	Microsoft Cosmos DB imitation API for MongoDB
Database support delivered directly by MongoDB engineers	Yes. Available with an optional support contract	No
Consulting services from engineers with direct access to internal MongoDB expertise	Yes. MongoDB Consulting Services	No

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