That's an interesting use case. I am not aware of any tools that would allow for such content-aware proxying of HTTP traffic with artificial latency introduced

That's an interesting use case. I am not aware of any tools that would allow for such content-aware proxying of HTTP traffic with artificial latency introduced in the response headers content parts separately. As of now, speedbump is protocol agnostic - it just proxies the data over TCP without analyzing it (I've used it to proxy HTTP, Postgres, Mongo and AMQP traffic). While the idea of delaying the last byte seems promising at the first glance, especially in the context of retaining protocol agnosticism, the issue is that the proxy doesn't really know which byte is the last one (unless it actually understands the traffic flowing through it - i.e. detecting end of the HTTP response). EDIT: You may want to look into echo-nginx-module, as it allows for adding timeouts between output flushed to the client. Perhaps it could be used in conjunction with NGINX's proxy module.