A web application is computer software or a program hosted on a web server that can be accessed over the Internet using web browsers. The web application does not need to be downloaded, but can be used online at any time, provided you have an internet connection and a web browser [1] [2]. The web application architecture describes the communication between the application, the server, and the database. The architecture of the application must ensure the efficient operation of the program, but also its security and user-friendliness [3]. The web application mainly consists of two parts: client-side code and server-side code [3]. Web applications are usually created with languages supported by web browsers, such as HTML, CSS, and JavaScript. These languages are mainly the front end of the application - everything that the user can visually see and use [1] [4]. The other side of the web application is its work logic and functions, ie the server and database side code. This part is called the backend [5]. In the backend, information is received from the user or frontend, this information is processed according to the code logic and the data received from the database, and the desired information is sent back to the user. However, there are more opportunities for backend development than the frontend [1] [6]. Most of the programming languages used today support web application backend development, such as Java, Python, C #, PHP, SQL, JavaScript, and many others [5]. Web application logic [edit] edit source] The user initiates a request that is sent to a web server over the Internet. For example, when logging in, the user enters a username and password and initiates a login request by clicking the "Login" button. The web server forwards the request to the web application server. An action corresponding to the received data is performed on the web application server, which returns the requested data. For example, the database is checked for such a username and the corresponding password. The web application server sends the processed data back to the web server. The web server returns the received data to the client, displaying the result in a web browser. For example, if the information entered by the user was correct, it will also be displayed in the web browser. This process occurs almost every time a user does something in a web application [4].