Designing a system like Twitter (X) in a system design interview involves outlining core functionalities such as composing and sharing tweets, following users, and favoriting tweets. Non-functional requirements like scalability, high availability, and stability are crucial for handling large-scale operations. Key aspects include capacity estimation, API design, database design, and understanding queries per second (QPS). Employing a structured approach and utilizing tools like Redis for caching, MySQL for data consistency, and Amazon S3 for media storage are essential. Detailed component design includes load balancers, CDNs, and handling failure scenarios to ensure robust system performance.