# Performance vs scalability

> From [The System Design Primer](https://github.com/donnemartin/system-design-primer) by Donne Martin, licensed under CC BY 4.0, arranged into chapters for this site. Part of "Core trade-offs". Web page: https://system.tangentbyte.com/learn/performance-vs-scalability

A service is **scalable** if it results in increased **performance** in a manner proportional to resources added. Generally, increasing performance means serving more units of work, but it can also be to handle larger units of work, such as when datasets grow.\<a href=[http://www.allthingsdistributed.com/2006/03/a_word_on_scalability.html>1](http://www.allthingsdistributed.com/2006/03/a_word_on_scalability.html%3E1)

Another way to look at performance vs scalability:

- If you have a **performance** problem, your system is slow for a single user.
- If you have a **scalability** problem, your system is fast for a single user but slow under heavy load.

### Source(s) and further reading

- [A word on scalability](http://www.allthingsdistributed.com/2006/03/a_word_on_scalability.html)
- [Scalability, availability, stability, patterns](http://www.slideshare.net/jboner/scalability-availability-stability-patterns/)