Azure eCommerce has a remarkably capable infrastructure to allow clients to scale their application up, down or horizontally. Another option would be to scale out their application, so that the Azure eCommerce instance can grow and adapt to the levels of visitor traffic that are coming into the application.
Various businesses are of a constantly evolving nature, where they may experience a peak usage time during a particular part of the day or week. Another possibility is a high or low season(s), where resources need to be scaled up, down or out, in order to successfully meet demand for the web application.
A beneficial aspect of Azure eCommerce is how it's sitting on an infrastructure that Microsoft has configured to be highly optimizable. Within software development, there's a general notion that it's usually less expensive to leverage more physical and virtualized resources than it is to build on the infrastructure side. Optimizing code and focusing on application development frequently abides by the law of diminishing returns; at some point it becomes logical to improve performance within the application.
On the other hand, there are a lot of low-hanging fruit capabilities within Azure itself, where the law of diminishing returns is consistently much less applicable. In most cases, you can get much more bang for your buck by improving the Microsoft Azure infrastructure optimization.