Ruby on Rails can be scalable, but it requires careful planning, optimization, and infrastructure management. As web traffic grows, developers may need to address performance bottlenecks and optimize database queries, caching, and asset management to ensure the application remains responsive. Horizontal scaling, which involves adding more servers to handle increased traffic, is a common approach for scaling Rails applications. Additionally, leveraging cloud services and content delivery networks (CDNs) can help improve performance and manage traffic growth.