Good practice with stdout to a webserver, to not saturate any actor

Question

First of all, maybe the architecture is wrong, and you can argue about that. But if not this question is relevant.

Here is a short description of the case:

disk ---> binary-reading ---> web-server ---> (Internet) ---> client
          on-disk-and         (aka cgi-bin                    (aka firefox)
          writing-to           running on
          stdout               Apache)

Reading huge files will saturate the web-server, which tries to transfer it to the client, which is also saturating (depends on the client, but Firefox does).

My question is more like:

How do posix console binaries when reading and writing on streams (disk, stdin, stdout) and chained together, not to saturate any intermediary actor? (cause here, if I read 100 Gb, I transfer 100 Gb++ in a raw)