Scaling JavaScript Applications for High Traffic

What are the key strategies for scaling JavaScript applications to handle high traffic and large data loads? Discuss the role of server-side rendering with frameworks like Next.js, caching mechanisms, and using CDNs (Content Delivery Networks) for static assets. How can developers optimize the front-end by minimizing JavaScript bundles, lazy loading resources, and using service workers for better performance? Additionally, what are the best practices for managing asynchronous data flows with technologies like GraphQL and WebSockets to ensure a smooth user experience under heavy loads?