[three14]

"Doesn't work how you'd expect" reminds me of the time that we had users receiving responses from other people's requests.

Why? Our API is idempotent, but we needed to use POST instead of GET to let the browser send a request body. Our API is very slow, so we put NGINX in front of our API to cache responses. We used something like proxy_cache_key "$request_uri|$request_body"; I don't think I was completely remiss in thinking that $request_body means "request body". Testing showed that it worked just fine. In production, some users made requests that were larger than our tests - and then $request_body is empty, and users will get each others' responses. This behavior is helpfully documented as follows:

"The variable’s value is made available in locations processed by the proxy_pass, fastcgi_pass, uwsgi_pass, and scgi_pass directives when the request body was read to a memory buffer."

Stackoverflow is more helpful: https://stackoverflow.com/questions/18795701/nginx-proxy-cac...