Modern JavaScript frameworks overcame the rendering performance limitations of Single-Page Applications (SPAs) by introducing Server-Side Rendering (SSR) and Static Site Generation (SSG). Unfortunately at the same time they created a potentially worse problem: unresponsive user interfaces. This is due to the need to hydrate UIs generated by SSR/SSG using client-side JavaScript before they can respond to user interactions. Recently frameworks have started to focus on this issue and tackle it using a variety of different approaches. These approaches include: React Server Components (RSC). islands of hydration, selective hydration, progressive enhancement, and resumability. In this talk I will describe these approaches, and highlight their benefits and limitations. This will enable you to determine which approach best meets your and your users needs.

The introduction of SSR and SSG have simultaneously been a big step forward and a big step back for Web performance. SPAs cannot achieve good startup rendering speed without SSR / SSG. But using these techniques often results in UIs that are initially unresponsive or slow to respond to user interactions. This is due to the requirement to hydrate such UIs before they can become interactive. Fortunately frameworks are now starting to tackle this limitation head-on using a variety of methods. I have investigated these methods, including interviewing their creators (Dan Abramove, Misko Hevery, Ryan Ryan Carniato, etc.), and this talk is a summary of what I have learned.