Proxy Buffering
Whether a reverse proxy accumulates a response before forwarding it, which protects the backend from slow clients but breaks streaming.
With buffering on, the proxy reads the full response from the backend quickly, freeing the backend's worker, and then delivers to the client at whatever rate the client manages. This protects backends from slow-client attacks and from long-lived connections tying up application threads.
With buffering off, bytes flow through as they are produced — which is required for server-sent events, streaming responses, long-polling and progressive rendering. Buffering silently breaks these: the client sees nothing until the response completes, which for an event stream means nothing at all.
The usual arrangement is buffering on by default, disabled per route for streaming endpoints.
Related settings that cause the same class of confusion: request body buffering (affects large uploads), and read/send timeouts, which terminate a legitimately long-lived stream unless raised for that route.