Scaling Simplified

Scaling referes to the ability of a software system to handle more requests by increasing the underlying infrastructure without hampering the performance of the application.

Let’s consider an example. Suppose you open a hotel with an initial capacity of 10 rooms. Since you are new in business, you don’t have many guests visiting your property and hence, your operations are run smoothly with this capacity.

Fast forward 6 months, now you are picking up pace and more guests come in on regular basis which causes delays in room availability. Theres’s chaos with guests queued in waiting leading to cacellations. At this point, your obvious step would be to increase capacity in order to handle the increase in demand.

To increase capacity, you can add more rooms to your hotel and in turn get more reservations. Say, instead of 10, you now have 20 rooms. This is called vertical scaling i.e. when the capacity of the given instance is increased to meet increased demand.

This setup will work efficiently until the demand increases again. With increase in demand, more rooms should be added. However, there’s a hard limit to the amount of load the foundation of your building can bear.

In order to solve this problem, you can add another building with 20 rooms and call it Wing B. The initial building will be Wing A. This is called horizontal scaling i.e. increasing capapcity by adding more instances similar to the existing one. In this way, all guests can be accomodated efficiently without putting exccessive load on the building foundation.

Now that the concept has been established, lets move on to the formal definition and key differences between horizontal and vertical scaling.