Scalability versus performance

It is quite easy to get confused between scalability and performance architectural concerns , because scalability is all about ensuring that, no matter the number of users consuming the application, all get the same pre-determined level of performance.

Performance relates to application features that ensure that the application caters to predefined response times and throughput. Scalability refers to having provisions for more resources when needed, to accommodate more users without sacrificing performance.

It is better to understand this using an analogy. The speed of a train refers to the performance of railway systems. However, accommodating more trains to run in parallel at the same or a higher speed will be referred to the scalability of the railway network.