What approach would you take to design a web application system for selling tickets?

This question aims to assess your comprehension of system design and your ability to analyze and explain the interactions between various components within a system. The interviewers are interested in evaluating your technical expertise, your understanding of web technologies, and your capability to create robust and scalable systems. In system design, you must consider multiple factors: system architecture, user interface design, database design, security protocols, performance and efficiency, as well as scalability. Additionally, you should outline how different components will interact and work together, manage various user requests, and address possible issues. Important points to keep in mind when responding to this question include: Outline the overall system architecture. Discuss the selected technologies and the reasons for their suitability. Clarify how session management will be handled, particularly in relation to users purchasing tickets and ensuring that no two users can buy the same ticket simultaneously. Describe how the application will manage load and ensure scalability. Identify potential challenges and explain how your system design addresses them.

A ticket-selling web application system primarily consists of three components: the Client-side, the Application Server, and the Database Servers. The **Client-side** is web-based, utilizing HTML, CSS, and JavaScript, allowing users to browse available events, select tickets, add them to their cart, and complete purchases. For the **Application Server**, I suggest using Node.js, as it is well-suited for managing multiple concurrent requests, a common requirement in ticket sales. Regarding the **Database Servers**, I recommend MySQL as the main database for storing data related to events, tickets, and transactions. Its transaction and locking features can effectively manage simultaneous ticket purchases. Lastly, it is essential to protect user data and payment transactions, potentially through HTTPS and third-party payment gateway services. To accommodate high traffic, implementing load balancing solutions like NGINX will be beneficial, and we should design the system to support horizontal scaling.

The design of a ticket sales web application must be both robust and efficient, capable of managing multiple requests simultaneously. I envision a three-tier architecture for this application, comprising the Presentation Layer (client-side user interfaces), Business Layer (the application server), and the Data Access Layer (databases). Presentation Layer : This layer includes the user interface, which I plan to develop using ReactJS because of its speed and efficiency. Business Layer : This layer encompasses all the business logic related to ticket sales. I would utilize Java and Spring Boot here due to their robustness and prevalent use in enterprise-level applications. Data Access Layer : For managing relational data such as user information, event details, and ticket data, I would opt for a SQL database like PostgreSQL. To provide a seamless user experience when numerous users attempt to purchase a limited number of tickets, implementing a queue or buffer, along with server-side validation, is essential to prevent overselling. Finally, it is crucial to ensure fast webpage loading times and to have a system that is both expandable and scalable, for which an AWS cloud solution could be beneficial. This would enable the application to handle high traffic periods and manage data backup and recovery effectively.