Cosmos DB APIs and Consistency Levels

Azure Cosmos DB is unique among databases in offering multiple wire-protocol-compatible APIs and five tuneable consistency levels. This lesson explores each API, when to use it, and how consistency levels let you make precise trade-offs between performance, availability, and data freshness.

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Cosmos DB APIs

When you create a Cosmos DB account, you choose an API. This choice is permanent — it cannot be changed after account creation.

NoSQL API (Native)

The NoSQL API (formerly called the SQL API or Core API) is Cosmos DB's native API. It stores data as JSON documents and uses a SQL-like query language:

SELECT c.name, c.email
FROM customers c
WHERE c.city = 'London'
ORDER BY c.name

Feature	Detail
Data format	JSON documents
Query language	SQL-like syntax with extensions
SDK support	.NET, Java, Python, Node.js, Go
Best for	New applications, general purpose
Unique features	Change feed, stored procedures, UDFs, triggers

The NoSQL API offers the broadest feature set and is the recommended choice for new applications.

MongoDB API