Copyright (c) 2026 MindMesh Academy. All rights reserved. This content is proprietary and may not be reproduced or distributed without permission.
4.2.1. Core Concepts: Global Distribution and Consistency
💡 First Principle: Cosmos DB trades simplicity and cost for global reach and performance guarantees. Unlike traditional databases that charge for storage, Cosmos DB charges primarily for throughput (Request Units)—you're paying for guaranteed performance, not just space.
Consistency Models (Critical Exam Topic!)
The fundamental trade-off in distributed systems is between consistency (everyone sees the same data) and latency (how fast you get a response). Cosmos DB offers five consistency levels allowing you to choose your position on this spectrum:
| Consistency Level | Guarantee | Latency | Use Case |
|---|---|---|---|
| Strong | Linearizable reads | Highest | Financial transactions |
| Bounded Staleness | Reads lag by defined time/versions | High | Need strong but can tolerate lag |
| Session | Consistent within a session | Medium | Most common; great for user sessions |
| Consistent Prefix | No out-of-order reads | Low | Messaging, feeds |
| Eventual | No ordering guarantees | Lowest | Analytics, logs |
Visual: Cosmos DB Global Distribution
Written byAlvin Varughese
Founder•15 professional certifications