Vertical vs horizontal scaling
Play this lessonThis lesson comes with an interactive animation you can break and a chapter quiz.⬆️ Vertical scaling ("scale up")
- Add more CPU and RAM to one server
- ✅ Very simple, no code changes
- ❌ Hard limit: you can't add infinite CPU
- ❌ No failover: if it dies, you're down
➡️ Horizontal scaling ("scale out")
- Add more servers to a pool
- ✅ Practically no ceiling
- ✅ One server dies, the others carry on
- ❌ Needs a way to spread traffic (next lesson)
When traffic is low, vertical scaling is a fine choice. For large applications, horizontal scaling wins because of the two limits above.
Key takeaways
- Vertical = bigger machine. Simple, but has a ceiling and no redundancy.
- Horizontal = more machines. The way large systems scale.