Azure Cosmos DB

Build globally distributed, multi-model databases with guaranteed latency.

⬢ TIER 2Tech

High

Salary impact

5 months

Time to learn

Medium

Difficulty

—

Careers

At a glance

Cosmos DB is Microsoft's globally distributed, multi-model database (document, key-value, graph, table). Database engineers earn $120-190k mid-level, essential for globally-scalable applications with low-latency requirements.

What is Azure Cosmos DB

Azure Cosmos DB is Microsoft's globally distributed, multi-model database providing SQL, MongoDB, Cassandra, Gremlin, and Table APIs. It guarantees <10ms latency at the 99th percentile, multi-region replication, and automatic failover. Global scale and low latency are increasingly critical. Cosmos DB is designed from the ground up for this. Key reasons:

🔧 TOOLS & ECOSYSTEM

Azure PortalAzure CLICosmos DB SDK (Python, Node.js, .NET)Data Explorer (Azure Portal)SQL API (SQL-like queries)Gremlin for graph queriesMongoDB API (MongoDB syntax)Table API (NoSQL table)Azure Functions (serverless integration)Azure Monitor

💰 Salary by region

Region	Junior	Mid	Senior
USA	$90k	$150k	$240k
UK	£74k	£123k	£195k
EU	€68k	€112k	€180k
CANADA	C$103k	C$171k	C$275k

❓ FAQ

Is Cosmos DB better than MongoDB?

Cosmos DB scales globally with low latency (single-digit milliseconds). MongoDB requires sharding and replication setup. Cosmos is managed; MongoDB requires operational overhead.

What is the pricing model?

Two options: provisioned throughput (pay for RU/s reserved) or serverless (pay per operation). Provisioned is cheaper for steady workloads; serverless for spiky.

Can I use Cosmos DB for ACID transactions?

Yes, multi-document ACID transactions within a partition. Cross-partition transactions are eventual consistent (limited). For strict ACID, use Azure SQL.

What are Request Units (RUs)?

Cosmos DB's throughput unit. 1 RU = resources to read 1 KB item. A query costs 5-10 RUs; a write costs 5+ RUs. Capacity planning around RU budget.

Can I use Cosmos DB with my existing MongoDB code?

Yes, via MongoDB API. Connect MongoDB drivers to Cosmos DB; most code works unchanged. Minor differences in some features.

How do I backup and restore?

Cosmos DB has continuous backup (30-day retention). Point-in-time restore to any point in window. No manual backup needed.

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