The difference between horizontal and vertical scaling

When dealing with system and cloud architecture, scalability remains a core concern. Being able to scale resources is important for handling traffic growth while maintaining performance and reliability.

In this regard, you may wonder how to distinguish between horizontal and vertical scaling — keep reading to find out.

A common real-world strategy involves mixing both horizontal and vertical scaling. This is called hybrid scaling, and is often considered the best approach.

Horizontal scaling (scaling out)

Horizontal scaling is about adding more nodes to handle load. In other words, you assign multiple machines to do the same job while balancing the load between them.

Advantages:

High scalability with a near-linear growth potential

Fault tolerance (a node can fail without the whole system going down)

Elastically scale out or in based on demand

Disadvantages:

Increased complexity

Requires additional operational overhead with monitoring, orchestration, and more

Not always cost-effective — can be overkill for many low-traffic systems

Vertical scaling (scaling up)

Vertical scaling, on the other hand, has to do with increasing the capacity of a single node. Instead of adding more machines to solve the same job, you assign more resources to that very same machine, making it increasingly more powerful.

Advantages:

Minimal architectural changes (easier to debug)

Lower operational complexity — there’s only one machine to deal with

Predictable behaviour, often at a cheaper cost

Disadvantages:

Hard upper limit in terms of hardware

Single point of failure (if the machine goes down, everything goes down)

Seldom cost-effective at scale

Conclusion

You’ve now learned about the most important advantages and disadvantages of horizontal and vertical scaling respectively.

Horizontal scaling is about adding more machines while vertical scaling is about a bigger machine — to put it simply. Although the fault tolerance of horizontal scaling sounds enticing, it’s often overkill for most projects, and can result in unwanted complexity.

If scalability is to be considered a strategy, the best course of action is to start small, and increase complexity along the way. Thus, hybrid scaling mixes the best of both worlds.

Thank you for reading.

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