Why do you use fetchQuery in router and not loadQuery?

[Dinno]

This might be a naive question. I just begin learning Relay. But it is not obvious why you don't load query and pass it's reference to the page but instead fetch and pass it's data directly.

[Dinno]

Perhaps it is connected to using it for SSR?

[koistya]

Yes, in order to being able access that data during full or partial (just section) SSR, see web/workers/proxy.ts -- a Cloudflare Worker script that resolves a URL path to a certain route, e.g. cosnt route = await resolveRoute({ path: "/users/john" }) and then injects page title, meta tags into the HTML page using that response from the router, containing fetchQuery payload. And also injects the serialized Relay store into the HTML <script id="data" type="application/json">...</script> so that when this page is being rendered in the browser, it doesn't have to maky any HTTP calls to the API during the initial (first) render.

[koistya]

BTW, it is possible to tweak the router it to either use fetchQuery or loadQuery depending on whether you need that data during server-side rendering or not.