Performance Vs Scalability

Performance and Scalability are two of the key aspects of software design. In my experience during most of the discussions about performance and scalability, a lot of people are often using these two words synonymously. In the reality, they mean different things.

Performance refers to the speed and effectiveness of a system under a given workload within a given time frame. In general terms, it measures how well software can perform its intended task. Achieving an acceptable level of performance is mandatory when developing software. So, performance is a software quality metric.?If we realize that our performance requirements got changed (e.g., serve more users, provide lower response times) or we cannot meet our performance goals, scalability comes into play.

Scalability refers to the characteristic of a system to increase performance by adding additional resources. Very often people think that their system is scalable out-of-the-box. “If we need to serve more users, we just add additional server”?is a typical answer for performance problems. However, this assumes that the system is scalable, meaning adding additional resources really helps to improve performance.?Software systems not having scalability as a design goal often do not provide good scalability.

Two kinds of scaling, Scaling vertically (scaling-up) means adding resources to a single machine. Increasing the number of available machines is called horizontal scaling (scaling out). Traditionally, adding more resources to the same server has been the preferred way of scaling but the requirements of modern applications are no more satisfied with available resource configurations and not feasible by the cost perspective also to the business. So, these days mostly scaling refers to the scaling out approach only.?

In summary, Applications and Platforms need to be designed with scaling in mind, such that adding resources results in improving the performance.

Refer to the below blog for more explanation with supermarket example https://blog.professorbeekums.com/performance-vs-scalability/