System Design
Horizontal Scaling
Handling more load by adding more servers, rather than making one server bigger.
Reviewed by the RadarTrek editorial team · June 2026
Horizontal scaling adds more machines to share the load (as opposed to vertical scaling, which makes one machine more powerful). It's the standard approach for web traffic because it has no hard ceiling — but it requires the app to be stateless, since requests can land on any server in the pool at any time.
Why it matters
- —Eliminating server-local state (in-memory sessions, local file uploads) is the real prerequisite — without it, horizontal scaling breaks in subtle ways.
- —Horizontal scaling pairs with a load balancer by necessity — more servers are useless if traffic isn't distributed across them.
- —Cloud autoscaling groups make horizontal scaling elastic — capacity grows and shrinks with real traffic instead of being fixed upfront.
Where to learn this
🎓
Load Balancing and Horizontal Scaling
System Design for Builders course
This is the exact lesson that covers this term in depth — with examples, diagrams, and a hands-on exercise.