Cosmos DB

In the Ultra Transcenders books

AZ-305AZ-700SC-500AI-300DP-900

Each book explains Cosmos DB in context, with comparison tables and the common traps.

Terms in this definition

• Non-relational database

  Stores data without imposing a relational schema. Common kinds: graph, column-family, document and key-value.

• Automatic indexing

  By default, Azure Cosmos DB indexes all properties of all items in a container, so you don't need to define a schema or maintain secondary indexes yourself. Paths can be left out through an indexing policy.

Related terms

• ACID

  Four promises a database transaction makes: atomicity, consistency, isolation and durability. Azure Cosmos DB honours them, with snapshot isolation, only inside one logical partition, using stored procedures, triggers or transactional batch.

• Agent memory

  The past conversation and knowledge an AI agent draws from it, such as summaries, facts and user profiles, saved so the agent keeps context from one turn or session to the next. Azure Cosmos DB and Azure Managed Redis are common places to keep it.

• Apache Gremlin

  The Apache TinkerPop language for traversing graphs. The matching Azure Cosmos DB API holds data as vertices (the nodes) linked by edges (the relationships), suiting cases where links between items matter, like social networks or recommendation engines.

• Azure Cosmos DB change feed

  An ordered log, kept persistently, of what changes in a Cosmos DB container. Event-driven designs use it: Azure Functions, for example, can read it and respond.

• Azure Cosmos DB Data Migration Tool

  Utility that moves data from sources such as SQL Server into Azure Cosmos DB.

• Azure DocumentDB

  Called Azure Cosmos DB for MongoDB (vCore) until its renaming on 18 November 2025, this managed MongoDB-compatible document database is now a service in its own right. It scales by vCores, whereas the separate Azure Cosmos DB for MongoDB uses request units.

• Azure Synapse Link for Cosmos DB

  Feature for querying Cosmos DB's analytical column store without ETL and without using request units from the transactional store. New projects can no longer adopt it and should use Cosmos DB mirroring in Microsoft Fabric.

• Azure Table Storage

  Holds structured NoSQL records without a fixed schema, using keys and attributes; think device details, contact lists or user records. It now sits within the Azure Cosmos DB family, where Azure Cosmos DB for Table is the premium step up.