Explore the challenges and techniques involved in migrating Pinterest profiles to React in this JSConf Budapest 2017 talk. Discover how to transition a high-traffic service to a new platform while maintaining functionality for millions of users. Learn about server-side JavaScript rendering, adapters for legacy data sources, and the evolution of web app architecture from Python Jinja to NodeJS Template rendering. Gain insights into the Denzel-React Bridge, reusing server-side HTML, and implementing Higher-Order Components as adapters. Understand the importance of A/B testing frameworks, experiment setups, and bottom-up approaches in large-scale migrations. Dive into the complexities of changing a live system's core components while ensuring seamless user experience.