Which of the following is considered a back-end issue?

Database connectivity is considered a back-end issue because it refers to the interactions between the server and the database where data is stored and managed. In web development, the back-end is responsible for handling the application's logic, database interactions, and server configurations. Proper database connectivity ensures that a web application can read from and write to the database, which is critical for managing data effectively. This includes establishing connections, executing queries, and ensuring data integrity during transactions. In contrast, user interface design, content management, and search engine optimization focus more on the presentation layer and user experience, which are aspects of the front-end and content handling rather than core back-end functionalities.