The server doesn't do any rendering before serving the page. All the "SSR" is done exactly once at build time. To the server it's no different from serving any other site.

I'm not too familiar with Gatsby but something has to be slowing you down if TTFB is too high.

It's not that high, Google says I might be able to save .8 seconds. I might try hosting on netlify and see if that improves things

An SSR React site IS simple HTML.

Doesn't matter, React has to rehydrate which blocks the CPU.

SSR solves waiting for the API but not the CPU problem.

That doesn't affect TTFB.

Ah you are right, my bad. I was thinking of TTFI.