Azure Cosmos DB
What it is: Azure's globally distributed, multi-model NoSQL database. One-click global replication, 99.999% availability, multiple consistency levels.
What It Does Best
Global distribution. Replicate to any Azure region with one click. Read/write data locally worldwide.
Multiple APIs. SQL, MongoDB, Cassandra, Gremlin, Table APIs. Migrate without rewriting apps.
Tunable consistency. Five consistency levels. Pick the right tradeoff for each operation.
Key Features
Turnkey global distribution: Multi-region writes with automatic failover
SLA guarantees: 99.999% availability, <10ms latency at P99
Five consistency models: Strong, bounded staleness, session, consistent prefix, eventual
Automatic indexing: All properties indexed by default, no schema required
Serverless option: Pay per request, auto-scaling to zero
Pricing
Provisioned: ~$0.00008 per RU/s-hour, 400 RU/s minimum (~$24/month)
Serverless: $0.25 per million operations, good for sporadic workloads
Autoscale: Scale between min and max RU/s automatically
Free tier: 1000 RU/s and 25GB storage free forever (one per account)
When to Use It
✅ Global applications requiring low latency worldwide
✅ Azure-native applications
✅ Migrating from MongoDB/Cassandra to cloud
✅ Mission-critical apps needing 99.999% uptime
✅ Applications with unpredictable scale (serverless mode)
When NOT to Use It
❌ Budget-constrained projects (can be expensive)
❌ Simple single-region apps (overkill)
❌ Complex analytics queries (use Synapse instead)
❌ Not on Azure (better alternatives exist)
❌ Need fine-grained cost control (RU billing complex)
Common Use Cases
Gaming: Player profiles, leaderboards, game state with global distribution
IoT: Device telemetry with global ingestion and local reads
Retail: Product catalogs and inventory across regions
Personalization: User profiles and preferences with low latency
Mobile apps: Backend for globally distributed mobile applications
Cosmos DB vs Alternatives
vs DynamoDB: Cosmos more flexible consistency, DynamoDB simpler pricing
vs MongoDB Atlas: Cosmos better Azure integration, MongoDB more mature ecosystem
vs Cassandra: Cosmos fully managed, Cassandra more control and cheaper
Unique Strengths
Multi-API support: Same database, multiple query interfaces
Industry-leading SLAs: Comprehensive guarantees on availability and latency
Global distribution simplified: Add regions with single button click
Automatic failover: Zero manual intervention during region failures
Bottom line: Premium globally distributed database for Azure. Exceptional availability and performance guarantees. Price scales quickly—monitor RUs carefully. Best for mission-critical global apps.