<strong>Horizontal scaling</strong> means adding more servers to handle traffic, while <strong>vertical scaling</strong> means making your existing server more powerful. Horizontal scales out (more machines), vertical scales up (bigger machine).
The Restaurant Analogy
Vertical scaling is like upgrading to a bigger kitchen with more equipment. Horizontal scaling is like opening multiple restaurant locations. Horizontal is usually better for web apps.
One Big Kitchen (Vertical)
Bigger stove, more chefs
Multiple Locations (Horizontal)
More restaurants
Customers (Traffic)
Need to be served
More Users
Horizontal or Vertical
Handle Load
Vertical: Upgrade hardware
Add more RAM, CPU, storage to one server
Horizontal: Add servers
Deploy identical copies of your app
Vertical: Limited by hardware
Eventually hit physical limits
Horizontal: Infinite scaling
Keep adding servers as needed
Horizontal needs load balancer
Distribute traffic across servers
Wrong
"Vertical scaling is always cheaper"
Correct
<strong>Horizontal scaling is often cheaper long-term</strong>. Vertical has limits and expensive hardware. Horizontal uses commodity servers and scales infinitely.
Netflix scaling:
Started with vertical scaling (bigger servers)
Hit limits during peak hours
Switched to horizontal scaling (thousands of servers)
Can now handle 200M+ users simultaneously