Programming

SSR is a overloaded term.

• There's SSR to help improve FCP (first contentful paint). This is not really so much an improvement to the client side framework as it is a crutch to workaround the fact that the frameworks are dynamically constructed clientside. But the first paint would just be Root node which is essentially empty. Because React and Vue are so heavily tied to the DOM structure, it expects to be the compositor of the tree, not something written in HTML. For pure HTML to be the compositor, you would need to add some rehydration to React/Vue to take a pre-composed state and reintegrate it into what React expects.

• SSR is also used to dynamically build content that is presented to the user that is not necessarily tied to rendering. This is popular with PHP, where instead of putting a blank table and then having the client fetch content over JS and then populate that table, the server just hands you the precompiled HTML. Not all the data as sent over JS may be useful (eg: only 10% is used after filtering and pagination), so to save transfer size and query latency, it may be the server that gets the always data from the store or cache. There's less client JS in execution, which may also help in performance.

• Then there's SSR for the purpose of improving SEO. This relates more to the first point, but maybe the first paint isn't important. Maybe client-side construction is plenty fast. But because the root is just blank, search engines that don't perform synchronous JavaScript can't actually read the content being shown to the user after all the rendering is said and done.

Personally, I've moved to Web Components that solves almost all of this. You can author layouts in HTML and anything that you want in your HTML file for SEO is included in the source. I would only use SSR to target the second issue, where you want to save on trips to build dynamic content. It is somewhat wasteful to give clients instructions to fetch and render when the server can do that on the first trip. The issue is rehydrating, or picking up from that state, but that truly depends on how complex your Web Components are. If they are sparse and simple enough, then all states should be able to be expressed over attributes. First paint can be reduced with the template shadow root, but I feel it's more trouble then it's worth and has negligible performance gains compared to just doing a prerender JS to register components and the browser will only render synchronously what's in the viewport anyway. That means time to first paint is not dependent of how big your page is. It's only dependent on how many elements you want to register before DOMContentLoaded.

From a financial aspect, I'm not about to ditch static CDNs to reinterpret nearly every single request with some server for SSR. The costs are nowhere near the same to try to reinterpret with SSR. You can micro-optimize to death with a SSR to CDN route and then hydrate, but I feel you risk complicating deployments to where you're so vendor-locked you have extra hoops to jump to make changes. God forbid you want to change frontend systems. At that point the DX pain is too much to justify and wanting to get out is inevitable.