Vertical vs Horizontal Scaling

Posted Aug 15, 2026 · 4 views

Vertical scaling makes the one machine bigger. Nothing about the application changes, which is why it is almost always the right first move — until you reach the largest machine that exists, or the reboot it takes to resize becomes downtime you cannot spend.

Horizontal scaling makes one machine into many. Capacity stops having a ceiling and one dead machine stops being an outage — in exchange for everything that gets harder once state is shared: sessions, caches, uploads, and every assumption that there is only one of you.

This reel is about *why there is more than one server*, not how the traffic gets divided between them.