We can handle up to MAX_USERS (64 by default) concurrently. Now, given that we don’t support CGI, it’s not a big deal. Gemini requests are small (up to 1024 bytes), and also the replies from the server are small (one line plus the document — if any), all over TLS obviously. (but even there, it’s lighter than HTTP because we don’t need to send the whole chain for the certificate — see TOFU). Given all the above, this doesn’t really improve the performance in the real world, but it’s nice to have. The main use case for this is to disallow slow clients to stop fast clients.

was copying BEFORE and not AFTER the ../.

apparently, on some systems there is a sendfile(2), so to avoid a name clash we rename it to send_file and send_dir.

it's the default, but just in case (since gemini spec explicitly talks about 1.3 as "default" and 1.2 for ease of implementation)