Editing Openai/692e1a61-9f08-800b-89a7-b2d4c506df31 (section)

===== A. Horizontal scalability and high throughput =====

Relational DBs (PostgreSQL, MySQL, SQL Server) can scale vertically (bigger box) reasonably well, and can do some read scaling with replicas. But at very high scale, sharding relational data is complex.

Many NoSQL systems are designed from the ground up to:
* Distribute data across many nodes (“sharding”) automatically
* Add capacity by adding more servers (scale-out, not just scale-up)
* Handle very high write and read throughput with predictable latency

Example: A high-traffic web app with millions of users and huge write rates (logging, clickstream, IoT signals) may find it much easier to meet throughput/latency requirements with a distributed NoSQL store than with a single relational instance.