Cloudflare ran a test and concluded that time to first byte (TTFB) does not matter.. Except, it absolutely does. As they say: if you're experiment contradicts intuition, check your experiment.

The problem is that it's not only the time that matters, but also what's in those first few bytes. If you're smart, then you first packet (1460 bytes), will  be able to flush just enough of your HTML head to allow the browser to begin the parsing and kick off resource prefetching: JavaScript, CSS, etc.

By doing this, while the TCP connection is still going through the slow-start phase, the browser can kick off the connections for blocking resources and consequently make the whole experience much faster.

Cloudflare's test is just silly. Of course it doesn't matter if you flush your '200 OK' after 1ms vs 1s - nothing magical there. But if you know what you're doing and craft the response right, then it can make a huge difference.

TL;DR: Time to First Byte Matters, when you know what to put into those bytes.
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