What is scaling?
In system Design terms, scaling is the process of increasing the system's performance and resources to handle more traffic or load without making it more complex.
There are two types of scaling:
Vertical Scaling (Scaling-up)
Horizontal Scaling (Scaling-out)
Vertical Scaling:
Vertical scaling is also known as scale-up, the process of increasing the system capacity or capabilities of an existing hardware or software component within a system. You can add more power to your system by adding a better processor, increasing RAM or making other changes. Vertical scaling aims to improve the performance and capacity of the system without changing the fundamental architecture or adding additional servers.
Pros of Vertical Scaling:
Ease Management - Vertical scaling generally involves upgrading a single node, which can be less complex.
Consistency - Single node avoids issues related to data distribution and consistency.
Increase Capacity - Upgrading hardware can increase capacity and performance.
Cons of Vertical scaling:
Limited scalability - Vertical scaling has physical limitations to how much you can upgrade a single machine or node.
Single point of failure - All requests are going to a single server, if the server fails it causes downtime.
Increase cost - High-performance hardware can be expensive.
Horizontal Scaling:
Horizontal scaling also known as scale-out, the process of increase the capacity or performance of a system by adding more machines or servers to distribute the workload across all nodes or units.
In horizontal scaling no need to change or replace the server we simply add more and more servers or machines to handle more requests.
Pros of Horizontal Scaling:
Increase capacity - More nodes can handle a larger number of requests.
Improve performance - Loads can be balanced on multiple nodes. So it improves the performance.
Increase fault tolerance - If one node fails requests will be redirected to other nodes, reducing downtime.
Cons of Horizontal Scaling:
Complexity - Managing more nodes or instances can be more complex than managing a single node.
Data inconsistency - Requests are distributed on multiple servers so there may be data inconsistency.
Increase cost - Adding more nodes or instances will be costly.
Which Scaling option is right for an application?
After a fair understanding of both options, we can see that both have some pros and cons. There will be always some tradeoffs, so its totally depends on your requirements, business goals and areas where you want to scale up.