Vertical scaling

1. Vertical scaling, or “scaling up”, refers to the process of adding more power (CPU, RAM, etc.) to existing servers.
2. When traffic is low, vertical scaling is a good simple option.
3. However, vertical scaling has a hard limit, since it is impossible to add unlimited CPU and memory to a single server.
4. Vertical scaling does not have failover and redundancy. If one server goes down, the whole website/app goes down with it completely.

Horiozontal scaling

1. Horizontal scaling, or “scaling out”, allows you to scale by adding more servers into your pool of resources.