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What is Horizontal Scalability?

Horizontal Scalability in IT and Development

As you might know, your app or system can handle a set number of simultaneous requests. If the demand exceeds this number, it won't be able to process further. When this happens, it's time for scaling! Scalability relates to how your system grows and adapts to change. If you find it's time to do this, you can choose between vertical and horizontal scaling. In this article, we'll cover the latter of the two: horizontal scalability. We'll explain what it entails, how it compares to vertical scalability, and when to use it. Let's dive in!

What is Horizontal Scalability?

Horizontal scalability entails adding nodes, computers, or database server racks to a system. Also called scaling out, it helps cope with new demands. As a result, several resources share the workload. Horizontal scalability allows for dealing with growing demands and adds complexity to your operation. Below, we'll look at the pros and cons of this type of scaling.

Benefits of Horizontal Scalability

- Resiliency. Several systems or database servers mean there is no single point of failure. Hence, horizontally scaled systems have good resistance to malfunction of a single instance. And, as data distributes across all nodes, the risk of losing any of it minimizes.

- Scaling. Regarding hardware, horizontal scalability simplifies the scaling process. Why? Well, you only need to add new machines to your current set. There is no need to check system requirements for upgrades on your existing devices.

- Downtime. When adding machines, switching off the existing ones is unnecessary when scaling. This procedure reduces or even cuts to zero downtime. Thus, upgrading processes are less likely to affect clients.

- Performance. Horizontal scaling entails several machines sharing the traffic node. With it, you can have more endpoints for connections. This method results in better network performance and security.

Disadvantages of Horizontal Scalability

- Maintenance. Maintaining one server or machine is more accessible than maintaining several. Also, horizontal scalability requires load balancing and potentially virtualization software.

- Costs. The initial cost of horizontal scalability is higher. The reason is that it involves buying new database servers or machines. Updating them through vertical scaling is more cost-effective.

Horizontal vs Vertical Scalability

We know what horizontal scalability is. Now it's time to meet its counterpart: vertical scalability—or scaling up. This method entails adding more resources or power to the same node, computer, or server. You can scale your memory, processing speed, or storage. Further examples of it are MongoDB, Cassandra, and Google Cloud Spanner. So, what else sets these two scaling methods apart? Let's look at their main differences. Both horizontal and vertical scaling have their pros and cons. Which one you choose will depend on your resources and your needs. Below, we'll share when it's best to choose one.

Horizontal Scalability Vertical Scalability
It entails splitting databases by adding new servers or machines It involves adding new resources with data remaining in a single node
Uupgrading is easier as you only need to add new appliances It’s harder to upgrade, and limitations on how much you can upgrade
As it requires load balancing, it's challenging to install and maintain It’s easy to implement and maintain as it entails a single system
It’s costly as it involves several machines across many data centers Since it involves just one device, it’s more cost-effective.
Horizontal scaling needs more time to implement Vertical scaling requires less time to implement
Great for increasing geographical range It can only offer a limited geographical presence
There is a lower probability of downtime It involves significant downtime rates
There is no limit to how many machines you can add to the system Scaling is limited, as a single device has a set capacity

On-Premise Scalability vs Cloud Scaling

There are alternatives beyond vertical and horizontal scalability! You can choose between on-premise and cloud scaling. Nowadays, cloud environments are becoming more and more common. So, they have gained a lot of ground on on-premise infrastructure. Horizontal scalability tends to be more popular when it comes to on-premise-based servers. Yet, vertical scalability is also possible in this case. In this context, cloud scaling can take place on horizontal and vertical scaling. Regardless of your choice, cloud scaling has the extra benefit of automatic scaling. This feature comes beyond its manual and scheduled scaling. Hence, it can be a great way to save both time and money, making the scaling process more straightforward.


Scalability is an indispensable aspect of any growing business. If you want to scale up your app or system, horizontal scalability is a great way. It simplifies the scaling process, improves performance, and decreases downtime. We hope this article has given you all the information you need to make the right choice.