How would you design Perplexity's system?

Focus on the key components of Perplexity's system, which is an AI-powered search engine that provides answers rather than just links. Break down the architecture into user input processing, natural language understanding, information retrieval, and answer generation. Discuss how you would handle data sources, including structured and unstructured data, and consider the algorithms for ranking and relevance. Address scalability and performance, particularly how the system can handle high traffic and provide quick responses. Finally, think about user experience and how to present information in a clear, concise manner.