I first ran into this years ago after working on a database client library as an intern. Having not heard of this option beforehand, I didn't think to enable it in the connections the library opened, and in practice that often led to messages in the wire protocol being entirely ready for sending without actually getting sent immediately. I only found out about it later when someone using it investigated why the latency was much higher than they expected, and I guess either they had run into this before or were able to figure out that it might be the culprit, and it turned out that pretty much all of the existing clients in other languages set NODELAY unconditionally.