Horizontal and vertical scaling are two fundamental approaches to increasing the capacity of a system to handle increased load or traffic.

Vertical Scaling (Scale Up) involves adding more resources to a single server, such as increasing CPU, RAM, or storage. This method is straightforward and often easier to implement, making it suitable for applications with low to moderate traffic. However, it has limitations, including a maximum capacity for each server and the risk of a single point of failure, where the entire application becomes unavailable if the server goes down. Additionally, upgrading to more powerful hardware can be costly ²³.

Horizontal Scaling (Scale Out), on the other hand, involves adding more servers or nodes to distribute the load across multiple instances. This approach allows for greater scalability, as you can add more nodes almost indefinitely. It is particularly effective for handling unpredictable loads and is commonly used in distributed systems. However, horizontal scaling can be more complex to implement due to the need for load balancers and coordination between nodes ²⁴.

In summary, the choice between horizontal and vertical scaling depends on the specific requirements of the application and the expected traffic patterns.