<p>ack-end architecture is the structure that supports the operations of a web application, focusing on the server, database, and APIs. The server processes incoming requests and serves data to the client, while the database stores and retrieves the data. The application logic, often handled by back-end frameworks like <strong>Express.js</strong>, <strong>Django</strong>, or <strong>Spring</strong>, connects the server to the database. Additionally, web services like <strong>RESTful APIs</strong> enable communication between the client and server. Key concerns in back-end architecture include <strong>scalability</strong>, <strong>security</strong>, and <strong>performance</strong> optimization.</p>