When you think about frequently accessed applications (the ones that we use daily), such as Google, YouTube, and Facebook, it is the performance of these applications that distinguishes them from similar applications. Think for a moment. If Google took more than 10 seconds to provide search results, most people would switch over to Bing or some other search engine. So, performance is one of the primary factors in an application's success.

In this chapter, we are going to learn about the following things:

Normally, when people talk about the performance of an application, they think about the application's speed. Though speed contributes significantly to the performance of the application, we also need to consider maintainability, scalability, and reusability of the application.

A well-maintained code will be clear and have less technical debt, which in turn will increase the productivity of the developer. When we write code based on service-oriented architecture or micro services, our code will be more usable by others. This would also make our code scalable.

Normally, people think about the performance of the application when they have almost completed the development of the application and pilot users are complaining about the speed of the application. The right time to discuss performance is before the development of the application; we need to work with the product owners, business analysts, and actual users in order to arrive at a standard of an acceptable level of performance for the application. Then we design and code with this expected level of performance as our goal.

This also depends on the domain of the application. For example, a mission-critical healthcare application would demand great performance (they might expect responses in less than a second), whereas the performance of a back-office application may not demand so much. So, it is critical to understand the domain in which we are working.

If you have been asked to tune the performance of an existing application, it is also important to understand the existing architecture of the application. With ASP.NET Core, you can build a simple CRUD application to a mission-critical application serving millions of users across the world. A large application might have many other components, such as a load balancer, separate caching servers, Content Delivery Networks (CDN), an array of slave DB servers, and so on. So, when you analyze the performance of the application, first you need to study architecture, analyze each of the individual components involved, measure the performance of each of the components, and try to optimize them when the application does not suit your acceptable performance. The main thing is not to jump into performance improvement techniques without studying and analyzing the architecture of the application. If you are creating a new application, you can think about performance right from the start of the application's creation.

We will examine a typical web application setup, shown in the following screenshot. We will then analyze it and consider how to improve it:

The following steps show the process of using a web application:

Thus, we can categorize these components into three layers—the UI layer, the web/application layer, and the DB layer. With respect to improving the overall performance of the ASP.NET Core application, we need to have a thorough look at how we can improve the performance of each of the layers.

Before implementing any performance improvement techniques, we need to first analyze the performance in each of the layers in the application. Only then can we suggest ways improve the overall performance of the application.